For neurologists and psychiatrists, this month's edition of CNS Spectrums contains both original research articles and review papers surrounding a central theme of enormous importance: how the environment can harm brain function and how the brain can repair itself. We are extremely fortunate to have Jeremy Coplan as our guest editor. Dr. Coplan, with whom I have enjoyed years of collaboration on many projects of mutual interest, is professor of psychiatry at the State University of New York (SUNY) Downstate Medical Center in Brooklyn and senior scientist in the Department of Clinical Psychobiology at the New York State Psychiatric Institute in New York City. Let me now summarize why I believe the area covered this month is so vital.