Neuroscientists have been mapping the physical anatomy of the human brain for over a century, but until recently researchers lacked a clear and comprehensive picture of which genes are used frequently and which are largely dormant in the myriad parts of this complex organ.

In 2012 a team at the Allen Institute for Brain Science in Seattle published the Allen Human Brain Atlas, which includes data on the activity of almost every gene at hundreds of locations inside the brains of five men and one woman. For comparison, the team had earlier produced an atlas of the mouse brain. The databases for these atlases, along with a viewer application called Brain Explorer, are freely available online.

This slide show presents some of the images developed by the Allen Institute in its studies of how the brain works in humans and mice. For more information on the Institute’s work, see “Genetic Maps of the Brain Lead to Surprises,” by Ed Lein and Mike Hawrylycz.