Squid

The nerve axon of the giant squid is nearly a millimeter thick, significantly larger than any nerve cells in humans. This fact permits researchers, neuroscientists in particular, to study the various aspects of nerve cell form and function with greater ease.

Because the brains of animals use similar chemical mechanisms for sending signals along their axons, studying the giant squid axon has provided the foundation for the understanding of how messages are transmitted in human brains, particularly the many roles played by ion channels in regulating activities in living cells.