Memory's Machine

A branching neuron inside a mouse's brain (right) is seen through a microscope that collects light from fluorescing proteins. Time-lapse images (left) of the two neural filaments in the yellow box reveal stable knobby spines (marked by yellow arrowheads) that may create lasting memories. Some protrusions (blue arrowhead) come and go daily as the brain rewires itself, while others (red arrowheads) last a few days longer. | Karel Svoboda