The Pappus chain is an infinite sequence of circles placed between two tangent circles.
Each new circle:
1. Touches the two main circles
2. Touches its neighboring circles
3. Becomes smaller and smaller
Although the number of circles increases forever, they all fit inside a finite space.
In 3D, the same idea creates an infinite chain of spheres between two larger spheres. mcdvoice
This construction beautifully shows how infinity can exist inside a bounded region.
Best Regard,
Max Martin