Scientists at UC San Francisco have created the first molecular-level, 3D picture of how an odor molecule activates a human odorant receptor. The breakthrough has been made using a type of imaging called cryo-electron microscopy (cryo-EM). Odorant receptors, which make up half of the largest, most diverse family of receptors in our bodies, are proteins that bind odor molecules on the surface of olfactory cells. The ability to map the interactions of thousands of scent molecules with hundreds of odorant receptors could allow a chemist to design a molecule and predict what it would smell like. The findings have been published in Nature.