 A number of human diseases (hereditary forms of myotonia, osteopetrosis, retinal degeneration, kidney stone diseases, epilepsy, deafness) could be mapped to mutations in specific ion channels.These fundamental insights allowed researchers to mimic important aspects of human diseases in genetically accurate animal models, a key step in the development of new drugs.More recently, ZMNH researchers developed novel genetic tools to control neuronal activity with light (optogenetics), including the first light-gated chloride channel ChloC and the light-activated potassium channel PACK.