Watch the full explainer from Sleep Science Space and discover why your brain needs deep rest to truly recover. The Science of Sleep Explained: What Your Brain Does at Night You can survive for weeks without food … but only days without sleep. Why? Each night, while you disappear from the world, your body begins the most complex repair cycle known to biology. Cells renew, memories reorganize, emotions untangle. Sleep is not wasted time — it is maintenance for being alive. Yet