diff --git a/README.md b/README.md
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@@ -39,4 +39,10 @@ To understand computer graphics better I will try to describe some important def
 
 By the end of this chapter I generated the following background:
 
-<img src="https://media.discordapp.net/attachments/1185146037774602320/1203455065361489920/image.png?ex=65d127de&is=65beb2de&hm=236433d19502d5b96e041838afe58191f4242f27a79abe32b8689ff80799b64c&=&format=webp&quality=lossless" alt="Second PPM image" width="480"/>
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+<img src="https://media.discordapp.net/attachments/1185146037774602320/1203455065361489920/image.png?ex=65d127de&is=65beb2de&hm=236433d19502d5b96e041838afe58191f4242f27a79abe32b8689ff80799b64c&=&format=webp&quality=lossless" alt="Second PPM image" width="480"/>
+
+### Chapter 4: Creating a sphere
+
+In this chapter I created a simple sphere and detect its surface by solving quadratic equations, which represent vectors. The sphere has no shading yet:
+
+<img src="https://media.discordapp.net/attachments/874752364698013736/1205930050038403072/image.png?ex=65da28e1&is=65c7b3e1&hm=26cef89e81f0810588599d6bf0db72b91b42d50789618968186b45459f501eb4&=&format=webp&quality=lossless" alt="Second PPM image" width="480"/>