When Südhof started his laboratory, he decided to switch from cholesterol metabolism to neuroscience, and to pursue a molecular characterization of synaptic transmission. His work initially focused on the mechanism of neurotransmitter release which is the first step in synaptic transmission, and whose molecular basis was completely unknown in 1986. Later on, Südhof's work increasingly turned to the analysis of synapse formation and specification, processes that mediate the initial assembly of synapses, regulate their maintenance and elimination, and determine their properties.