Genes and photons: new avenues into the neuronal basis of behavior.

A convergence of advances in optical methods and a better understanding of the genetics of development promise to revolutionize the study of neuronal circuits and their links to behavior. One of the great challenges in systems neurobiology has been to monitor and perturb activity in populations of identified neurons in vivo. Recent work has begun to achieve this goal through a combination of modern imaging methods with genetic labeling and perturbation.