How our brains work is one of the major unsolved problems of biology. This paper describes some of the techniques of molecular biology that are already being used to study the brains of animals. Mainly as a result of the human genome project many new techniques will soon become available which could decisively influence the progress of neuroscience. I suggest that neuroscientists should tell molecular biologists what their difficulties are, in the hope that this will stimulate the production of useful new biological tools.