Neurotransmitter release is an example of exocytosis, the secretion of material by cells from membrane-bound vesicles that fuse with the plasma membrane. We also use analytical and computational methods to study membrane fusion and release of other substances vital for the life of a multi-cellular organism, including hormones such as insulin, cytokines in the immune system and enzymes. Misregulation of exocytosis is associated with disease, for example misregulated insulin release in diabetes. Compared to neurotransmitter secretion, the vesicles involved are larger and the fusion and release processes slower.