What makes a child decide to become a scientist? •For Robert Sapolsky–Stanford professor of biology–it was an argument with a rabbi over a passage in the Bible. •Physicist Lee Smolin traces his inspiration to a volume of Einstein’s work, picked up as a diversion from heartbreak. •Mihaly Csikszentmihalyi, a psychologist and the author of Flow, found his calling through Descartes. Murray Gell-Mann, Nicholas Humphrey, Freeman Dyson . . . 27 scientists in all write about what it was that sent them on the path to their life's work. Illuminating memoir meets superb science writing in stories that invite us to consider what it is–and what it isn’t–that sets the scientific mind apart.