Using new technology, scientists have catalogued more than 20,000 brain cells in one region of the mouse hypothalamus. The study revealed some 50 distinct cell types, including a previously undescribed neuron type that may underlie some of the genetic risk of human obesity. This catalog of cell types marks the first time neuroscientists have established a comprehensive "parts list" for this area of the brain. The new information will allow researchers to establish which cells play what role in this region of the brain.