Our research group is dedicated to understand the molecular basis of human diseases using structural biology, which allows us to visualize how proteins function or malfunction at the atomic level. A major area of our research concerns the structure and function of botulinum neurotoxins (BoNTs), which are among the most poisonous substances known to humans. BoNTs therefore represent a major bioterrorist threat. Paradoxically, BoNT-containing medicines and cosmetics have been used with great success in clinic. Both the toxic and therapeutic functions of BoNTs indeed rely on a common mechanism to enter motoneurons, cleave SNAREs that mediate release of acetylcholine, and subsequently paralyze the affected muscles. We are trying to understand the molecular mechanisms underlying the BoNT-host interplay. These studies will help to improve clinical efficacy of BoNT-containing drugs, suggest novel therapeutic applications for BoNTs, and guide the development of effective anti-BoNT strategies. In parallel, we are striving to understand the structural mechanisms underlying synapse formation, neurotransmission, and synaptic plasticity, which may facilitate the design and improvement of therapeutic agents for the treatment of some psychological and neurological disorders.