In the centuries-old quest to unlock the mysteries of the human mind, thousands of specimens of actual gray matter have been collected, jarred, and analyzed in laboratories and hospitals around the world.

From these collections, scientists came to understand some crucial details. Preserved mammalian brains revealed just how similar the human brain is to other animals; studying Einstein’s preserved brain gave insights into the differences in visual, mathematical, and spatial processing; a suffragist’s donated brain helped prove that a woman’s brain is just as well-developed as a man’s. Here are eight fascinating displays of preserved brains that can be visited today.