diff --git a/src/abacus-kochka/README.md b/src/abacus-kochka/README.md
index cb9c9d5b48..813366dafc 100644
--- a/src/abacus-kochka/README.md
+++ b/src/abacus-kochka/README.md
@@ -1,5 +1,8 @@
 [![Crowdin](https://badges.crowdin.net/kochkacommx/localized.svg)](https://crowdin.com/project/kochkacommx)
 
+- https://kochka.com.mx/
+- [PageSpeed Insights](https://pagespeed.web.dev/report?url=https%3A%2F%2Fkochka.com.mx%2Fmenu&form_factor=mobile)
+
 ```text
 yarn install
 yarn dev
diff --git a/src/abacus-kochka/pages/_document.js b/src/abacus-kochka/pages/_document.js
index 3023b053c3..b8967b1529 100644
--- a/src/abacus-kochka/pages/_document.js
+++ b/src/abacus-kochka/pages/_document.js
@@ -15,10 +15,10 @@ type RenderPageResult = {
 
 export default class MyDocument extends Document {
   // See: https://nextjs.org/docs/advanced-features/custom-document#customizing-renderpage
-  static async getInitialProps({ renderPage }: DocumentContext): Promise<RenderPageResult> {
-    const page = await renderPage();
-    return { ...page, styles: [sx.getStyleTag()] };
-  }
+  // static async getInitialProps({ renderPage }: DocumentContext): Promise<RenderPageResult> {
+  //   const page = await renderPage();
+  //   return { ...page, styles: [sx.getStyleTag()] };
+  // }
 
   createGoogleAnalyticsMarkup(): { __html: string } {
     return {
diff --git a/src/sx/README.md b/src/sx/README.md
index ce7612d613..46ffaf3fd9 100644
--- a/src/sx/README.md
+++ b/src/sx/README.md
@@ -13,6 +13,7 @@ In conventional applications, CSS rules are duplicated throughout the stylesheet
   - [Automatic vendor prefixes](#automatic-vendor-prefixes)
 - [Server-side rendering](#server-side-rendering)
 - [Architecture](#architecture)
+  - [Runtime styles architecture](#runtime-styles-architecture)
 - [Prior Art](#prior-art)
 
 ## Installation and Usage
@@ -480,6 +481,14 @@ Internally, these steps are happening:
 
 5. and finally, we collect the values of the final object and print them as `className`
 
+### Runtime styles architecture
+
+Runtime styles are styles that were not rendered by server (are for whatever reason missing or SSR is not enabled). Here is how SX deals with this situation:
+
+1. SX tries to find `<style data-adeira-sx />` (or creates it if it doesn't exist yet) and does "rehydration" where it goes through the existing styles and remembers which ones are already applied.
+2. SX performs runtime injection of the styles while checking whether the styles already exist or not.
+3. The rest is the same.
+
 ## Prior Art
 
 _sorted alphabetically_
diff --git a/src/sx/src/StyleCollector.js b/src/sx/src/StyleCollector.js
index d08942cafd..42dcf95c5a 100644
--- a/src/sx/src/StyleCollector.js
+++ b/src/sx/src/StyleCollector.js
@@ -3,6 +3,7 @@
 import { invariant, warning } from '@adeira/js';
 
 import expandShorthandProperties from './expandShorthandProperties';
+import printNodes from './printNodes';
 import StyleCollectorAtNode from './StyleCollectorAtNode';
 import StyleCollectorPseudoNode from './StyleCollectorPseudoNode';
 import { type StyleCollectorNodeInterface } from './StyleCollectorNodeInterface';
@@ -41,7 +42,7 @@ class StyleCollector {
   #styleBuffer: StyleBufferType = new Map();
   #keyframes: Map<string, string> = new Map();
 
-  collect(baseStyleSheet: { +[sheetName: string]: $FlowFixMe }): {
+  collectStylesheets(baseStyleSheet: { +[sheetName: string]: $FlowFixMe }): {
     +hashRegistry: HashRegistryType,
     +styleBuffer: StyleBufferType,
   } {
@@ -106,23 +107,17 @@ class StyleCollector {
     };
   }
 
-  print(): string {
-    let sxStyle = '';
-    this.#styleBuffer.forEach((node) => {
-      sxStyle += node.printNodes({ trailingSemicolon: true }).join('');
-    });
-    this.#keyframes.forEach((node) => {
-      sxStyle += node;
-    });
-    return sxStyle;
+  collectKeyframe(name: string, value: string): void {
+    this.#keyframes.set(name, value);
   }
 
-  addKeyframe(name: string, value: string): boolean {
-    if (this.#keyframes.has(name)) {
-      return true;
-    }
-    this.#keyframes.set(name, value);
-    return false;
+  // TODO: remove
+  print(): string {
+    // TODO: print keyframes as well
+    //     this.#keyframes.forEach((node) => {
+    //       sxStyle += node;
+    //     });
+    return printNodes([...this.#styleBuffer]);
   }
 
   reset(): void {
diff --git a/src/sx/src/StyleCollectorAtNode.js b/src/sx/src/StyleCollectorAtNode.js
index aed2fa19f3..d448c9473c 100644
--- a/src/sx/src/StyleCollectorAtNode.js
+++ b/src/sx/src/StyleCollectorAtNode.js
@@ -43,15 +43,11 @@ export default class StyleCollectorAtNode implements StyleCollectorNodeInterface
     this.nodes = new Map([...this.nodes, ...nodes]);
   }
 
-  getAtRuleName(): string {
-    return this.atRuleName;
+  getNodes() {
+    return this.nodes;
   }
 
-  printNodes(config?: PrintConfig): $ReadOnlyArray<string> {
-    let output = '';
-    this.nodes.forEach((node) => {
-      output += node.printNodes({ ...config, bumpSpecificity: true }).join('');
-    });
-    return [`${this.atRuleName}{${output}}`];
+  getAtRuleName(): string {
+    return this.atRuleName;
   }
 }
diff --git a/src/sx/src/StyleCollectorNode.js b/src/sx/src/StyleCollectorNode.js
index 304face3cb..97f5206241 100644
--- a/src/sx/src/StyleCollectorNode.js
+++ b/src/sx/src/StyleCollectorNode.js
@@ -37,7 +37,11 @@ export default class StyleCollectorNode implements StyleCollectorNodeInterface {
 
   // eslint-disable-next-line no-unused-vars
   addNodes(nodes: Map<string, StyleCollectorNodeInterface>) {
-    invariant(false, 'StyleCollectorNode cannot have nested nodes,');
+    invariant(false, 'StyleCollectorNode cannot have nested nodes.');
+  }
+
+  getNodes(): Map<string, StyleCollectorNode> {
+    invariant(false, 'StyleCollectorNode cannot have nested nodes.');
   }
 
   getHash(): string {
@@ -52,11 +56,16 @@ export default class StyleCollectorNode implements StyleCollectorNodeInterface {
     return this.styleValue;
   }
 
-  printNodes(config?: PrintConfig): $ReadOnlyArray<string> {
-    const className = `.${this.hash}`.repeat(config?.bumpSpecificity === true ? 2 : 1);
-    const pseudo = config?.pseudo ?? '';
-    const trailingSemicolon = config?.trailingSemicolon ? ';' : '';
+  // printNodes(config?: PrintConfig): $ReadOnlyArray<string> {
+  //   const className = `.${this.hash}`.repeat(config?.bumpSpecificity === true ? 2 : 1);
+  //   const pseudo = config?.pseudo ?? '';
+  //   const trailingSemicolon = config?.trailingSemicolon ? ';' : '';
+  //
+  //   return [`${className}${pseudo}{${this.styleName}:${this.styleValue}${trailingSemicolon}}`];
+  // }
 
-    return [`${className}${pseudo}{${this.styleName}:${this.styleValue}${trailingSemicolon}}`];
+  // CSSStyleRule.selectorText
+  rehydrationIdentifier() {
+    return `.${this.getHash()}`;
   }
 }
diff --git a/src/sx/src/StyleCollectorNodeInterface.js b/src/sx/src/StyleCollectorNodeInterface.js
index f1deea8086..dfcc235752 100644
--- a/src/sx/src/StyleCollectorNodeInterface.js
+++ b/src/sx/src/StyleCollectorNodeInterface.js
@@ -8,5 +8,5 @@ export type PrintConfig = {
 
 export interface StyleCollectorNodeInterface {
   addNodes(nodes: Map<string, StyleCollectorNodeInterface>): void;
-  printNodes(config?: PrintConfig): $ReadOnlyArray<string>;
+  getNodes(): Map<string, StyleCollectorNodeInterface>;
 }
diff --git a/src/sx/src/StyleCollectorPseudoNode.js b/src/sx/src/StyleCollectorPseudoNode.js
index 0b8fd56d74..4af737bd8e 100644
--- a/src/sx/src/StyleCollectorPseudoNode.js
+++ b/src/sx/src/StyleCollectorPseudoNode.js
@@ -1,5 +1,7 @@
 // @flow strict
 
+import type { AllCSSPseudoTypes } from './css-properties/__generated__/AllCSSPseudoTypes';
+import StyleCollectorNode from './StyleCollectorNode';
 import type { PrintConfig, StyleCollectorNodeInterface } from './StyleCollectorNodeInterface';
 
 /**
@@ -23,29 +25,40 @@ import type { PrintConfig, StyleCollectorNodeInterface } from './StyleCollectorN
  *   ],
  * }
  * ```
+ *
+ * Note that nesting pseudo classes is not allowed in SX.
  */
 export default class StyleCollectorPseudoNode implements StyleCollectorNodeInterface {
   pseudo: string;
-  nodes: Map<string, StyleCollectorNodeInterface>;
+  nodes: Map<string, StyleCollectorNode>;
 
-  constructor(pseudo: string, nodes: Map<string, StyleCollectorNodeInterface>) {
+  constructor(pseudo: $Keys<AllCSSPseudoTypes>, nodes: Map<string, StyleCollectorNode>) {
     this.pseudo = pseudo;
     this.nodes = nodes;
   }
 
-  addNodes(nodes: Map<string, StyleCollectorNodeInterface>) {
+  addNodes(nodes: Map<string, StyleCollectorNode>) {
     this.nodes = new Map([...this.nodes, ...nodes]);
   }
 
+  getNodes(): Map<string, StyleCollectorNode> {
+    return this.nodes;
+  }
+
   getPseudo(): string {
     return this.pseudo;
   }
 
-  printNodes(config?: PrintConfig): $ReadOnlyArray<string> {
-    let output = [];
-    this.nodes.forEach((node) => {
-      output = output.concat(node.printNodes({ ...config, pseudo: this.pseudo }));
-    });
-    return output;
-  }
+  // printNodes(config?: PrintConfig): $ReadOnlyArray<string> {
+  //   let output = [];
+  //   this.nodes.forEach((node) => {
+  //     output = output.concat(node.printNodes({ ...config, pseudo: this.pseudo }));
+  //   });
+  //   return output;
+  // }
+
+  // CSSStyleRule.selectorText
+  // rehydrationIdentifier() {
+  //   return `.${this.getHash()}`;
+  // }
 }
diff --git a/src/sx/src/__tests__/printNodes.test.js b/src/sx/src/__tests__/printNodes.test.js
new file mode 100644
index 0000000000..7bd22028d3
--- /dev/null
+++ b/src/sx/src/__tests__/printNodes.test.js
@@ -0,0 +1,78 @@
+// @flow
+
+import printNodes from '../printNodes';
+import StyleCollectorAtNode from '../StyleCollectorAtNode';
+import StyleCollectorNode from '../StyleCollectorNode';
+import StyleCollectorPseudoNode from '../StyleCollectorPseudoNode';
+
+it('prints `StyleCollectorNode` as expected', () => {
+  expect(
+    printNodes([
+      new StyleCollectorNode('color', 'red'),
+      new StyleCollectorNode('color', 'green'),
+      new StyleCollectorNode('color', 'blue'),
+    ]),
+  ).toMatchInlineSnapshot(`
+    "._324Crd{color:#f00}
+    .mRoJ3{color:#008000}
+    ._2dHaKY{color:#00f}"
+  `);
+});
+
+it('prints `StyleCollectorPseudoNode` as expected', () => {
+  expect(
+    printNodes([
+      new StyleCollectorPseudoNode(
+        ':hover',
+        new Map([
+          // TODO: are the map keys necessary (?)
+          ['c0', new StyleCollectorNode('color', 'red')],
+          ['c1', new StyleCollectorNode('color', 'green')],
+          ['c2', new StyleCollectorNode('color', 'blue')],
+        ]),
+      ),
+    ]),
+  ).toMatchInlineSnapshot(`
+    "._324Crd:hover{color:#f00}
+    .mRoJ3:hover{color:#008000}
+    ._2dHaKY:hover{color:#00f}"
+  `);
+});
+
+it('prints `StyleCollectorAtNode` as expected', () => {
+  expect(
+    printNodes([
+      new StyleCollectorAtNode(
+        '@media screen',
+        new Map([
+          ['c0', new StyleCollectorNode('fontSize', '14')],
+          [
+            'c1',
+            new StyleCollectorPseudoNode(
+              ':hover',
+              new Map([['c0', new StyleCollectorNode('color', 'pink')]]),
+            ),
+          ],
+
+          [
+            'c2',
+            new StyleCollectorAtNode(
+              '@media (max-width: 12cm)',
+              new Map([['c0', new StyleCollectorNode('color', 'blue')]]),
+            ),
+          ],
+        ]),
+      ),
+    ]),
+  ).toMatchInlineSnapshot(`
+    "@media screen{
+    ._1fVgat._1fVgat{font-size:14}
+    ._3ncx7d._3ncx7d:hover{color:#ffc0cb}
+    @media (max-width: 12cm){
+    ._2dHaKY._2dHaKY{color:#00f}
+    }
+    }"
+  `);
+});
+
+// TODO: prefixing
diff --git a/src/sx/src/__tests__/rehydrateStyles.test.js b/src/sx/src/__tests__/rehydrateStyles.test.js
new file mode 100644
index 0000000000..b5b661737e
--- /dev/null
+++ b/src/sx/src/__tests__/rehydrateStyles.test.js
@@ -0,0 +1,58 @@
+/**
+ * @flow
+ * @jest-environment jsdom
+ */
+
+/* global document */
+
+import { invariant } from '@adeira/js';
+
+import rehydrateStyles from '../rehydrateStyles';
+
+it('correctly rehydrates styles from a style element', () => {
+  // First, we need to create a `CSSStyleSheet` by actually creating a style element:
+  const styleElement = document.createElement('style');
+  document.head?.appendChild(styleElement);
+  const styleSheet = styleElement.sheet;
+
+  invariant(styleSheet != null, 'Unable to create test StyleSheet.');
+
+  // Insert some simple CSS rules:
+  styleSheet.insertRule('._2tPCgL { font-size: 10px; }', 0);
+  styleSheet.insertRule('._1Kmfck:hover { color: rgba(var(--sx-foreground), 0.5); }', 1);
+
+  // Insert some @at rules:
+  styleSheet.insertRule(
+    `@media (prefers-reduced-motion: reduce) { .VdrO3.VdrO3 { animation-duration: 1s; } }`,
+    2,
+  );
+  styleSheet.insertRule(
+    `@media (prefers-reduced-motion: reduce) { ._2tPCgL._2tPCgL { font-size: 10px; } }`,
+    3,
+  );
+  styleSheet.insertRule(
+    `@keyframes oxCh9 { 33% { transform: translateY(-10px); } 66% { transform: translateY(10px); } }
+  `,
+    4,
+  );
+
+  // We should be able to decide whether the style needs to be injected later based on the
+  // following information:
+  expect(rehydrateStyles(styleSheet)).toMatchInlineSnapshot(`
+    Object {
+      "rehydratedKeyframeRules": Set {
+        "oxCh9",
+      },
+      "rehydratedMediaRules": Map {
+        "(prefers-reduced-motion: reduce)" => Set {
+          ".VdrO3.VdrO3",
+          "._2tPCgL._2tPCgL",
+        },
+      },
+      "rehydratedStyleRules": Set {
+        "._2tPCgL",
+        "._1Kmfck:hover",
+      },
+    }
+  `);
+});
diff --git a/src/sx/src/create.js b/src/sx/src/create.js
index 240807f692..3ee948e7ed 100644
--- a/src/sx/src/create.js
+++ b/src/sx/src/create.js
@@ -3,7 +3,9 @@
 import { invariant, isBrowser, isObjectEmpty, isObject } from '@adeira/js';
 import levenshtein from 'fast-levenshtein';
 
+import getStyleSheetFromStyleTag from './getStyleSheetFromStyleTag';
 import injectRuntimeStyles from './injectRuntimeStyles';
+import rehydrateStyles from './rehydrateStyles';
 import styleCollector from './StyleCollector';
 import type { AllCSSPropertyTypes } from './css-properties/__generated__/AllCSSPropertyTypes';
 import type { AllCSSPseudoTypes } from './css-properties/__generated__/AllCSSPseudoTypes';
@@ -48,10 +50,12 @@ export default function create<T: SheetDefinitions>(sheetDefinitions: T): Create
     `Function 'sx.create' cannot be called with empty stylesheet definition.`,
   );
 
-  const { hashRegistry, styleBuffer } = styleCollector.collect(sheetDefinitions);
+  const { hashRegistry, styleBuffer } = styleCollector.collectStylesheets(sheetDefinitions);
 
   if (isBrowser()) {
-    injectRuntimeStyles(styleBuffer);
+    const styleSheet = getStyleSheetFromStyleTag();
+    const rehydratedRules = rehydrateStyles(styleSheet);
+    injectRuntimeStyles(styleSheet, rehydratedRules, styleBuffer);
   }
 
   function sxFunction(maybeObject, ...styleSheetsSelectors) {
diff --git a/src/sx/src/getStyleSheetFromStyleTag.js b/src/sx/src/getStyleSheetFromStyleTag.js
new file mode 100644
index 0000000000..c63ef740b6
--- /dev/null
+++ b/src/sx/src/getStyleSheetFromStyleTag.js
@@ -0,0 +1,40 @@
+// @flow
+
+/* global document */
+
+import { invariant } from '@adeira/js';
+
+// <style data-adeira-sx />
+opaque type StyleElementType = HTMLStyleElement | null;
+let styleAdeiraSXTag: StyleElementType = null;
+
+/**
+ * This function will try to get already existing `<style data-adeira-sx />` HTML tag or it will
+ * create a new virtual one in case it doesn't exist yet.
+ */
+export default function getStyleSheetFromStyleTag(): CSSStyleSheet {
+  if (styleAdeiraSXTag === null) {
+    styleAdeiraSXTag = ((document.querySelector('style[data-adeira-sx]'): any): StyleElementType);
+    if (styleAdeiraSXTag === null) {
+      // Still `null` so let's create the style element:
+      const htmlHead = document.head;
+      styleAdeiraSXTag = document.createElement('style');
+      styleAdeiraSXTag.type = 'text/css';
+      styleAdeiraSXTag.setAttribute('data-adeira-sx', '');
+      /* $FlowFixMe[incompatible-call] This comment suppresses an error when
+       * upgrading Flow. To see the error delete this comment and run Flow. */
+      htmlHead?.appendChild(styleAdeiraSXTag);
+    }
+  }
+
+  /* $FlowFixMe[incompatible-use] This comment suppresses an error when
+   * upgrading Flow. To see the error delete this comment and run Flow. */
+  const styleSheet = styleAdeiraSXTag.sheet;
+
+  invariant(
+    styleSheet != null,
+    'SX cannot apply runtime styles because HTMLStyleElement.sheet does not exist.',
+  );
+
+  return styleSheet;
+}
diff --git a/src/sx/src/getStyleTag.js b/src/sx/src/getStyleTag.js
index ccee12bc2c..3192f48d2d 100644
--- a/src/sx/src/getStyleTag.js
+++ b/src/sx/src/getStyleTag.js
@@ -11,6 +11,7 @@ import StyleCollector from './StyleCollector';
  */
 export default function getStyleTag(): Element<'style'> {
   const createStylesMarkup = () => {
+    // TODO: do not run `serialize` again here
     const cssStyles = serialize(compile(StyleCollector.print()), middleware([prefixer, stringify]));
     return { __html: cssStyles };
   };
diff --git a/src/sx/src/injectRuntimeStyles.js b/src/sx/src/injectRuntimeStyles.js
index 0774ded921..dd88dbdc12 100644
--- a/src/sx/src/injectRuntimeStyles.js
+++ b/src/sx/src/injectRuntimeStyles.js
@@ -1,58 +1,33 @@
 // @flow
 
-/* global document */
-
-import { invariant, warning } from '@adeira/js';
+import { warning } from '@adeira/js';
 import { compile, serialize, stringify, prefixer, middleware } from 'stylis';
 
 import StyleCollectorAtNode from './StyleCollectorAtNode';
 import StyleCollectorNode from './StyleCollectorNode';
 import StyleCollectorPseudoNode from './StyleCollectorPseudoNode';
+import {
+  printStyleCollectorAtNode,
+  printStyleCollectorNode,
+  printStyleCollectorPseudoNode,
+} from './printNodes';
+import type { RehydratedStyles } from './rehydrateStyles';
 import type { StyleBufferType } from './StyleCollector';
 
-// <style data-adeira-sx />
-opaque type StyleElementType = HTMLStyleElement | null;
-let styleAdeiraSXTag: StyleElementType = null;
-
-const getStyleTag = (): CSSStyleSheet => {
-  if (styleAdeiraSXTag === null) {
-    styleAdeiraSXTag = ((document.querySelector('style[data-adeira-sx]'): any): StyleElementType);
-    if (styleAdeiraSXTag === null) {
-      // Still `null` so let's create the style element:
-      const htmlHead = document.head;
-      styleAdeiraSXTag = document.createElement('style');
-      styleAdeiraSXTag.type = 'text/css';
-      styleAdeiraSXTag.setAttribute('data-adeira-sx', '');
-      /* $FlowFixMe[incompatible-call] This comment suppresses an error when
-       * upgrading Flow. To see the error delete this comment and run Flow. */
-      htmlHead?.appendChild(styleAdeiraSXTag);
-    }
-  }
-
-  /* $FlowFixMe[incompatible-use] This comment suppresses an error when
-   * upgrading Flow. To see the error delete this comment and run Flow. */
-  const styleSheet = styleAdeiraSXTag.sheet;
-
-  invariant(
-    styleSheet != null,
-    'SX cannot apply runtime styles because HTMLStyleElement.sheet does not exist.',
-  );
-
-  return styleSheet;
-};
-
-function hasStyleRule(match: (CSSRule) => boolean) {
-  const styleSheet = getStyleTag();
-  for (const cssRule of styleSheet.cssRules) {
-    if (match(cssRule)) {
-      return true;
+export function injectRuntimeKeyframes(
+  styleSheet: CSSStyleSheet,
+  rehydratedRules: RehydratedStyles,
+  css: string,
+  name: string,
+) {
+  const hasStyleRule = (match: (CSSRule) => boolean) => {
+    for (const cssRule of styleSheet.cssRules) {
+      if (match(cssRule)) {
+        return true;
+      }
     }
-  }
-  return false;
-}
-
-export function injectRuntimeKeyframes(css: string, name: string) {
-  const styleSheet = getStyleTag();
+    return false;
+  };
 
   const matchFunction = (cssRule) => {
     if (cssRule.type === CSSRule.KEYFRAMES_RULE) {
@@ -63,7 +38,9 @@ export function injectRuntimeKeyframes(css: string, name: string) {
   };
 
   if (hasStyleRule(matchFunction) === false) {
+    // TODO: leverage rehydrated rules
     const rules = [];
+    // TODO: get rid of this:
     serialize(compile(css), middleware([prefixer, (rule) => rules.push(rule)]));
 
     rules.forEach((rule) => {
@@ -73,44 +50,57 @@ export function injectRuntimeKeyframes(css: string, name: string) {
 }
 
 // https://developer.mozilla.org/en-US/docs/Web/API/CSS_Object_Model
-export default function injectRuntimeStyles(styleBuffer: StyleBufferType) {
-  const styleSheet = getStyleTag();
-
-  const matchFunction = (node) => (cssRule) => {
-    if (cssRule.type === CSSRule.STYLE_RULE) {
-      const styleRule = ((cssRule: any): CSSStyleRule);
-      if (styleRule.selectorText === `.${node.getHash()}`) {
-        return true;
-      }
-    }
-    return false;
-  };
-
+export default function injectRuntimeStyles(
+  styleSheet: CSSStyleSheet, // TODO: note: we are mutating this
+  { rehydratedStyleRules, rehydratedMediaRules, rehydratedKeyframeRules }: RehydratedStyles,
+  styleBuffer: StyleBufferType,
+) {
   styleBuffer.forEach((node) => {
     const insertIndex = styleSheet.cssRules.length;
 
     if (node instanceof StyleCollectorNode) {
-      if (hasStyleRule(matchFunction(node)) === false) {
-        // apply missing styles
-        const rule = serialize(
-          compile(node.printNodes({ trailingSemicolon: true }).join('')),
-          middleware([prefixer, stringify]),
+      const rehydrationIdentifier = node.rehydrationIdentifier();
+      if (rehydratedStyleRules.has(rehydrationIdentifier) === false) {
+        // Apply the missing styles:
+        styleSheet.insertRule(
+          printStyleCollectorNode(node, { trailingSemicolon: true }),
+          insertIndex,
         );
-        styleSheet.insertRule(rule, insertIndex);
+
+        // Register the rule into rehydrated styles, so we don't attempt to process it again:
+        rehydratedStyleRules.add(rehydrationIdentifier);
       }
     } else if (node instanceof StyleCollectorAtNode) {
-      // TODO: make sure we are not adding already added styles (?)
-      const rule = serialize(
-        compile(node.printNodes({ trailingSemicolon: true }).join('')),
-        middleware([prefixer, stringify]),
-      );
-      styleSheet.insertRule(rule, insertIndex);
-    } else if (node instanceof StyleCollectorPseudoNode) {
-      const nodes = node.printNodes({ trailingSemicolon: true });
-      for (const nodeElement of nodes) {
-        // TODO: make sure we are not adding already added styles (?)
-        const rule = serialize(compile(nodeElement), middleware([prefixer, stringify]));
+      // TODO: leverage rehydrated rules (to add only new rules)
+      // TODO: media queries & keyframe rules
+      const rehydrationIdentifier = node.getAtRuleName().replace(/.*(\(.+\)).*/, '$1');
+
+      // TODO: we probably has to dig a bit deeper and check whether the @at rule has every inner rule applied
+      if (rehydratedMediaRules.has(rehydrationIdentifier) === false) {
+        const rule = printStyleCollectorAtNode(node, { trailingSemicolon: true });
         styleSheet.insertRule(rule, insertIndex);
+
+        // TODO: Register the rule into rehydrated styles, so we don't attempt to process it again:
+        rehydratedMediaRules.set(
+          rehydrationIdentifier,
+          node.getNodes(), // TODO: ???
+        );
+      }
+    } else if (node instanceof StyleCollectorPseudoNode) {
+      for (const [, testNode] of node.getNodes()) {
+        // TODO: better
+        const rehydrationIdentifier = `${testNode.rehydrationIdentifier()}:${node.getPseudo()}`;
+        if (rehydratedStyleRules.has(rehydrationIdentifier) === false) {
+          styleSheet.insertRule(
+            printStyleCollectorNode(testNode, {
+              pseudo: node.getPseudo(),
+            }),
+            insertIndex,
+          );
+        }
+
+        // TODO: Register the rule into rehydrated styles, so we don't attempt to process it again:
+        rehydratedStyleRules.add(rehydrationIdentifier);
       }
     } else {
       warning(false, 'Node not supported in runtime styles: %j', node);
diff --git a/src/sx/src/keyframes.js b/src/sx/src/keyframes.js
index 869da83ce2..a1ce04af68 100644
--- a/src/sx/src/keyframes.js
+++ b/src/sx/src/keyframes.js
@@ -1,14 +1,16 @@
 // @flow
 
 import { isBrowser, nullthrows } from '@adeira/js';
-import stringify from 'json-stable-stringify';
+import stringifyStable from 'json-stable-stringify';
 
+import getStyleSheetFromStyleTag from './getStyleSheetFromStyleTag';
 import hash from './hashStyle';
-import type { AllCSSPropertyTypes } from './css-properties/__generated__/AllCSSPropertyTypes';
+import rehydrateStyles from './rehydrateStyles';
 import styleCollector from './StyleCollector';
 import transformStyleName from './transformStyleName';
 import transformStyleValue from './transformValue';
 import { injectRuntimeKeyframes } from './injectRuntimeStyles';
+import type { AllCSSPropertyTypes } from './css-properties/__generated__/AllCSSPropertyTypes';
 
 type KeyFrames = {
   +from?: AllCSSPropertyTypes,
@@ -30,10 +32,27 @@ const extractStyles = (styles: AllCSSPropertyTypes) => {
 
 const transformKey = (key: string) => key.replace(/\s/g, '');
 
+/**
+ * Helper function generating animation name. Usage:
+ *
+ * ```js
+ * const bounce = sx.keyframes({
+ *    '33%': { transform: `translateY(-1.4em)` },
+ *    '66%': { transform: `translateY(1.4em)` },
+ * });
+ *
+ * const styles = sx.create({
+ *    svgCircle: {
+ *      animationName: bounce,
+ *    }
+ *    // …
+ * });
+ * ```
+ */
 export default function keyframes(styleDefinitions: KeyFrames): string {
   let cssDefinition = '';
   // `from{maxHeight:0,opacity:0}` should be the same as `from{opacity:0,maxHeight:0}`
-  const parsedDefinitions: KeyFrames = JSON.parse(stringify(styleDefinitions));
+  const parsedDefinitions: KeyFrames = JSON.parse(stringifyStable(styleDefinitions));
 
   for (const key of Object.keys(parsedDefinitions)) {
     const styleValue = nullthrows(parsedDefinitions[key]);
@@ -42,13 +61,12 @@ export default function keyframes(styleDefinitions: KeyFrames): string {
 
   const name = hash(cssDefinition);
   const frame = `@keyframes ${name} {${cssDefinition}}`;
-  const exists = styleCollector.addKeyframe(name, frame);
+  styleCollector.collectKeyframe(name, frame);
 
-  if (isBrowser() && !exists) {
-    // It is possible that the keyframe was added on the server
-    // The StyleCollector will return false, but the injectRuntimeKeyframes checks
-    // If the rule is already added, so it won't be duplicated
-    injectRuntimeKeyframes(frame, name);
+  if (isBrowser()) {
+    const styleSheet = getStyleSheetFromStyleTag();
+    const rehydratedRules = rehydrateStyles(styleSheet);
+    injectRuntimeKeyframes(styleSheet, rehydratedRules, frame, name);
   }
 
   return name;
diff --git a/src/sx/src/printNodes.js b/src/sx/src/printNodes.js
new file mode 100644
index 0000000000..7184cb3639
--- /dev/null
+++ b/src/sx/src/printNodes.js
@@ -0,0 +1,83 @@
+// @flow
+
+import { compile, middleware, prefixer, serialize, stringify } from 'stylis';
+
+import StyleCollectorAtNode from './StyleCollectorAtNode';
+import StyleCollectorNode from './StyleCollectorNode';
+import StyleCollectorPseudoNode from './StyleCollectorPseudoNode';
+
+const STYLESHEET_SEPARATOR = '\n';
+
+/**
+ * This function takes care of the correct rendering of each node. Additionally, it takes care of
+ * browser prefixing.
+ */
+export default function printNodes(
+  nodes: $ReadOnlyArray<StyleCollectorAtNode | StyleCollectorNode | StyleCollectorPseudoNode>,
+) {
+  const printedRules = [];
+  for (const node of nodes) {
+    if (node instanceof StyleCollectorNode) {
+      printedRules.push(printStyleCollectorNode(node));
+    } else if (node instanceof StyleCollectorPseudoNode) {
+      printedRules.push(printStyleCollectorPseudoNode(node));
+    } else if (node instanceof StyleCollectorAtNode) {
+      printedRules.push(printStyleCollectorAtNode(node));
+    } else {
+      // TODO: invariant
+    }
+  }
+
+  const stylesheet = printedRules.join(STYLESHEET_SEPARATOR);
+  // TODO: make sure this is the only place we are calling `serialize` as it would not be optimal (performance wise)
+  return serialize(compile(stylesheet), middleware([prefixer, stringify]));
+}
+
+export function printStyleCollectorNode(node: StyleCollectorNode, config = {}) {
+  const pseudo = config.pseudo ?? '';
+  const withIncreasedSpecificity = config.increaseSpecificity ?? false;
+
+  const selectorText = `.${node.getHash()}`.repeat(withIncreasedSpecificity === true ? 2 : 1);
+  const selectorTextWithPseudo = `${selectorText}${pseudo}`;
+
+  // TODO: apply `serialize` in case it's called directly without `printNodes`
+  return `${selectorTextWithPseudo}{${node.getStyleName()}:${node.getStyleValue()}}`;
+}
+
+export function printStyleCollectorPseudoNode(pseudoNode: StyleCollectorPseudoNode, config = {}) {
+  const withIncreasedSpecificity = config.increaseSpecificity ?? false;
+  const printedRules = [];
+  for (const [, node] of pseudoNode.getNodes()) {
+    printedRules.push(
+      printStyleCollectorNode(node, {
+        pseudo: pseudoNode.getPseudo(),
+        increaseSpecificity: withIncreasedSpecificity,
+      }),
+    );
+  }
+
+  // TODO: apply `serialize` in case it's called directly without `printNodes`
+  return printedRules.join(STYLESHEET_SEPARATOR);
+}
+
+export function printStyleCollectorAtNode(atNode: StyleCollectorAtNode) {
+  const printedAtRules = [];
+  for (const [, node] of atNode.getNodes()) {
+    if (node instanceof StyleCollectorNode) {
+      printedAtRules.push(printStyleCollectorNode(node, { increaseSpecificity: true }));
+    } else if (node instanceof StyleCollectorPseudoNode) {
+      printedAtRules.push(printStyleCollectorPseudoNode(node, { increaseSpecificity: true }));
+    } else if (node instanceof StyleCollectorAtNode) {
+      printedAtRules.push(
+        printStyleCollectorAtNode(node, {
+          increaseSpecificity: true, // Should the specificity be increased even more for nested at rules?
+        }),
+      );
+    } else {
+      // TODO: invariant
+    }
+  }
+
+  // TODO: apply `serialize` in case it's called directly without `printNodes`
+  return `${atNode.getAtRuleName()}{\n${printedAtRules.join(STYLESHEET_SEPARATOR)}\n}`;
+}
diff --git a/src/sx/src/rehydrateStyles.js b/src/sx/src/rehydrateStyles.js
new file mode 100644
index 0000000000..146361ee52
--- /dev/null
+++ b/src/sx/src/rehydrateStyles.js
@@ -0,0 +1,79 @@
+// @flow
+
+import { warning } from '@adeira/js';
+
+// Unique entries are identified by the style selector text ("._XYZ"  or "._XYZ:hover").
+let rehydratedStyleRules = null;
+
+// Unique entries are a combination of the media condition text ("(prefers-color-scheme: light)")
+// and selector text of each rule in the media rule ("._XYZ"  or "._XYZ:hover").
+let rehydratedMediaRules = null;
+
+// Unique entries are identified by the keyframe name ("_XYZ").
+let rehydratedKeyframeRules = null;
+
+export type RehydratedStyles = {
+  rehydratedStyleRules: Set<string>,
+  rehydratedMediaRules: Map<string, Set<string>>,
+  rehydratedKeyframeRules: Set<string>,
+};
+
+/**
+ * This function goes through already existing stylesheet inside `<style data-adeira-sx />` and
+ * register what CSS rules are already rendered by the server (rehydration). This information is
+ * later used by `injectRuntimeStyles` and `injectRuntimeKeyframes` to inject only (runtime) styles
+ * that do not exist yet.
+ */
+export default function rehydrateStyles(styleSheet: CSSStyleSheet): RehydratedStyles {
+  if (
+    // memoize so we call this only once to populate the values
+    rehydratedStyleRules === null ||
+    rehydratedMediaRules === null ||
+    rehydratedKeyframeRules === null
+  ) {
+    rehydratedStyleRules = new Set();
+    rehydratedMediaRules = new Map();
+    rehydratedKeyframeRules = new Set();
+
+    for (const cssRule of styleSheet.cssRules) {
+      if (cssRule.type === CSSRule.STYLE_RULE) {
+        const cssStyleRule = ((cssRule: any): CSSStyleRule);
+        rehydratedStyleRules.add(cssStyleRule.selectorText); // "._XYZ"  or "._XYZ:hover"
+      } else if (cssRule.type === CSSRule.MEDIA_RULE) {
+        const cssMediaRule = ((cssRule: any): CSSMediaRule);
+        const cssMediaRuleText = cssMediaRule.media.mediaText;
+        const collectedMediaSelectorTexts = new Set();
+        for (const cssMediaNestedRule of cssMediaRule.cssRules) {
+          collectedMediaSelectorTexts.add(((cssMediaNestedRule: any): CSSStyleRule).selectorText);
+        }
+        if (rehydratedMediaRules.has(cssMediaRuleText)) {
+          rehydratedMediaRules.set(
+            cssMediaRuleText,
+            new Set([
+              ...(rehydratedMediaRules.get(cssMediaRuleText) ?? new Set()),
+              ...collectedMediaSelectorTexts,
+            ]),
+          );
+        } else {
+          rehydratedMediaRules.set(cssMediaRuleText, collectedMediaSelectorTexts);
+        }
+      } else if (cssRule.type === CSSRule.KEYFRAMES_RULE) {
+        const cssKeyframesRule = ((cssRule: any): CSSKeyframesRule);
+        rehydratedKeyframeRules.add(cssKeyframesRule.name); // "_XYZ"
+      } else {
+        warning(
+          false,
+          'Could not rehydrate the following CSS style (type %s): %s',
+          cssRule.type,
+          cssRule.cssText,
+        );
+      }
+    }
+  }
+
+  return Object.freeze({
+    rehydratedStyleRules,
+    rehydratedMediaRules,
+    rehydratedKeyframeRules,
+  });
+}