On Easter Saturday 1921, pharmacologist Otto Loewi dreamed of an experiment that would prove that the transmission of nerve impulses was chemical rather than electrical. He scribbled down the idea and went back to sleep, then discovered the next morning that he couldn’t read the note.

That day, he said, was the longest of his life. Fortunately, the dream returned to him that night, and this time he went immediately to the laboratory. Thirteen years later he received the Nobel Prize for discovering the role of acetylcholine as an endogenous neurotransmitter.