Simplicial sphere

A simplicial sphere is like a ball made out of flat surfaces. Imagine cutting out shapes like triangles, squares, and pentagons from a piece of paper. Then you can connect the edges of the shapes to make a three-dimensional ball! This ball is called a simplicial sphere. Just like a soccer ball has pentagons and hexagons on its surface, a simplicial sphere has flat pieces (or "simplices") that fit together perfectly to make a ball-like shape. That's why it's called a "sphere"! Scientists use simplicial spheres to study things like the shape of the universe and how things stick together. Pretty cool, huh?