The reason we need sleep has long mystified scientists, but it’s crystal clear that we do need it. In fact, the more we learn about what happens while we snooze, the more we discover new benefits for multiple processes including hormone balance, immune function, emotional health, learning, and memory. Studies show that even one night of disturbed rest leads to measurable impairments, and for this minicollection, we’ve gathered the most recent research on the mechanisms of sleep.