diff --git a/package-lock.json b/package-lock.json
index 13346f6..8b0c4e0 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -12,7 +12,8 @@
         "@emotion/styled": "^11.14.1",
         "@mui/material": "^9.0.1",
         "react": "^19.2.6",
-        "react-dom": "^19.2.6"
+        "react-dom": "^19.2.6",
+        "zod": "^4.4.3"
       },
       "devDependencies": {
         "@eslint/js": "^10.0.1",
@@ -3472,7 +3473,6 @@
       "version": "4.4.3",
       "resolved": "https://registry.npmjs.org/zod/-/zod-4.4.3.tgz",
       "integrity": "sha512-ytENFjIJFl2UwYglde2jchW2Hwm4GJFLDiSXWdTrJQBIN9Fcyp7n4DhxJEiWNAJMV1/BqWfW/kkg71UDcHJyTQ==",
-      "dev": true,
       "license": "MIT",
       "funding": {
         "url": "https://github.com/sponsors/colinhacks"
diff --git a/package.json b/package.json
index 73b191c..aca2bdb 100644
--- a/package.json
+++ b/package.json
@@ -15,7 +15,8 @@
     "@emotion/styled": "^11.14.1",
     "@mui/material": "^9.0.1",
     "react": "^19.2.6",
-    "react-dom": "^19.2.6"
+    "react-dom": "^19.2.6",
+    "zod": "^4.4.3"
   },
   "devDependencies": {
     "@eslint/js": "^10.0.1",
diff --git a/src/App.tsx b/src/App.tsx
index 1127eb0..0e818e0 100644
--- a/src/App.tsx
+++ b/src/App.tsx
@@ -1,12 +1,78 @@
-import { CssBaseline, Typography } from '@mui/material';
+import { z } from 'zod'
+// TODO: Use Material UI later.
+// TODO: Improve error-handling. Introduce some proper server response.
+
+type ImageId = string
+type ImageRef = string
+ 
+type Image = {
+  id: ImageId,
+  dimension: Dimension,
+  source: ImageRef, 
+}
+
+type Dimension = {
+  width: number,
+  height: number,
+}
+
+// WARNING: page starts at 1
+type Pagination = {
+  page: number,
+  limit: number, // page size
+}
+
+const Pagination = {
+  init(): Pagination { return { page: 1, limit: 10 } },
+}
+
+
+// === api ===
+const picsumApiImageSchema = z.object({
+  id: z.string(),
+  author: z.string(),
+  width: z.number(),
+  height: z.number(),
+  url: z.string(),
+  download_url: z.string(), // WARNING: the api-endpoint returns "url" and "download_url". You definitely want "download_url" for image sources.
+})
+type PicsumApiImage = z.infer<typeof picsumApiImageSchema>
+
+async function getPicsumImages({ page, limit }: Pagination): Promise<PicsumApiImage[]> {
+  const response = await fetch(`https://picsum.photos/v2/list?limit=${limit}&page=${page}`)
+  if (!response.ok) {
+    throw new Error(`Failed to fetch images: ${response.status}`)
+  }
+
+  const json: unknown = await response.json()
+  const data = z.array(picsumApiImageSchema).parse(json)
+
+  return data
+}
+
+async function getImages(pagination: Pagination): Promise<Image[]> {
+  const data = await getPicsumImages(pagination)
+  return data.map(({ id, download_url, width, height }) => ({ id: id as ImageId, dimension: { width, height }, source: download_url as ImageRef }))
+}
+
+async function getImageIds(pagination: Pagination): Promise<ImageId[]> {
+  const data = await getPicsumImages(pagination)
+  return data.map(({ id }) => id)
+}
+
+// Use this for `<img src=... />`
+function getImageSource(id: ImageId, dimension: Dimension): ImageRef {
+  return `https://picsum.photos/id/${id}/${dimension.width}/${dimension.height}`;
+}
+
+// test
+// (async () => {
+//   const imgs = await getImages({ page: 2, limit: 10 })
+//   console.log(imgs)
+// })()
 
 export default function App() {
   return (
-    <>
-      <CssBaseline />
-      <main>
-        <Typography variant="h1">Hello world</Typography>
-      </main>
-    </>
-  );
+    <h1>hello world</h1>
+  )
 }