“In a way, it’s startling how universal sleep is: In the midst of the hurried scramble for survival, across eons of bloodshed and death and flight, uncountable millions of living things have laid themselves down for a nice, long bout of unconsciousness. … Whatever sleep gives to the sleeper is worth tempting death over and over again, for a lifetime.” Reporter Veronique Greenwood visits a lab in Japan where scientists are trying to find the answer(s) to this question.