If a change is as good as a rest, neuroscientists should be the most relaxed people around. Even the study of normal brain function is the study of a dynamic, changing system; but more profound alterations occur in the developing, aging or diseased brain, and the investigation of these processes is at the core of modern neuroscience.

Change is a constant theme in this month's issue. Mark Johnson takes us on a tour of the developing cognitive world of the human infant, and discusses three theories that attempt to link postnatal neural development with emerging cognitive skills. Vincent Wang and Huda Zoghbi, on the other hand, focus on the molecular basis of the development of the cerebellum, as revealed by genetic techniques.

Long-term developmental changes contrast with the shorter-term, cyclical changes described by Ruud Buijs and Andries Kalsbeek, who look at the circadian clocks used by organisms to adapt to a 24-hour cycle. Discussing change on a still shorter timescale, Danny Winder and David Sweatt champion the cause of the serine/threonine phosphatases in synaptic plasticity. Once thought of as the humble housekeepers of phosphorylation, tidying up after the more glamorous kinases, phosphatases are emerging as key players in the regulation of synaptic transmission.

Diseases also involve change, albeit of a different nature. Two proteins, α-synuclein and the metalloproteinases, have been implicated in the devastating damage associated with various neurodegenerative diseases, as discussed by Michel Goedert and Wee Yong et al. Those reported masters of change, stem cells, may offer new hope for treating neurodegenerative diseases; but after evaluating the evidence for stem cell plasticity, Sally Temple concludes that much work remains to be done before we can say with certainty that these cells will live up to their billing.