On picking up this first volume of a new series of books the reader may ask the two questions: (a) why research methods? and (b) why in neurochem­ istry? The answers to these questions are easy - they more than justify the volumes to come and show the strong need for their existence. It is customary to think of methods as a necessary but unexciting means to an end - to relegate advances in methodology to a minor role in the creative, original portion of advances in science. This is not the case; the pace-setting function of methodology is well illustrated in most areas of neurobiology. To formulate our questions to Nature (which is the essence of experimental design), methodology is needed; to get answers to our ques­ tions we have to devise yet new methods. The chapters of the present volume fully illustrate how the development of a new method can cut a new path­ how it can open new fields, just as the microscope founded histology. Heter­ ogeneity of structures presents a formidable challenge for methodology in the nervous system, yet methods for separating the structures are essential if we ever want to decipher the enigma of functional contribution of the ele­ ments to the whole. The problem is not only physical separation-clearly methods are essential to study complex structures in situ.