In this issue:
"Perchance to Prune": Connections among nerve cells grow weaker during sleep, which seems to aid memory.
"Why Exercise Works Magic": Being active is good for many reasons beyond the old familiar ones.
"What Is Real?": The world may consist of bundles of properties, such as color and shape.
"The Surprising Origins of Life’s Complexity": Scientists are exploring how organisms can evolve elaborate structures without Darwinian selection.