Venn diagrams

When I learned about Venn diagrams as a kid, they usually had only two or three rings, or sets. But here's one with six sets by John Venn himself:

Here's another one, by A. W. F. Edwards:

I learned this from Venn diagram on Wikipedia.

See also: A Survey of Venn Diagrams, which has a lot of math that is way, way over my head, but also some cool images.

Image credits:
1. top image: Wikimedia commons, originally by Kopophex
2. bottom image: Wikimedia commons