British biologists Alan Hodgkin and Andrew Huxley discovered the resting potential in the summer of 1939, while studying marine invertebrates—sea creatures that lack a spine, such as clams, squid, and lobsters (Stevens, 1971). Hodgkin and Huxley worked with the squid giant axon because it is 100 times larger than the biggest axon in humans. They inserted a thin wire into the squid axon so that it touched the jellylike fluid inside. Then they placed another wire just outside the axon in the watery fluid that surrounds it. They found a substantial difference between the electric charges inside and outside the axon, which they called the resting potential.

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