In this review we start with a historical perspective beginning with the early morphological work done almost 50 years ago. The importance of these pioneering studies is underscored by our brief summary of the key questions addressed by subsequent research into the mechanism of secretion. We then highlight important advances in our understanding of the formation and maturation of neuroendocrine secretory granules, first using in vitro reconstitution systems, then most recently biochemical approaches, and finally genetic manipulations in vitro and in vivo.