The Drosophila larval neuromuscular junction (NMJ) has become one of the most powerful model systems to ask key neurobiological questions. This synapse is unparalleled by its accessibility, its simplicity, and the ability to manipulate genes important for synapse development and function. Its synapses have properties shared by many organisms including humans. The vast majority of genes that when mutated cause congenital disorders of the nervous system in humans, are present in the fruit fly genome, and fly models of human disorders are available. Thus, this preparation is a powerful tool to understand the normal function of these genes. This book reviews outstanding work by recognized leaders in the fields of Drosophila cellular neurogenetics including developmental neurobiology, mechanisms of synaptic function, and experience dependent changes at synapses. The book also includes step-by-step protocols to study the cellular biology of the NMJ, making it a vital resource for researchers beginning their investigations with this system, for those who are training students and postdoctoral fellows in this area, or simply as a general reference material for neuroscientists and neuroscience professors in general.