This image shows distinct neural connections in a cross section of a mouse's hippocampus, a region of the brain involved in the memory of facts and events. The large, crescent-shaped area in green is hippocampal zone CA1. Its highly specialized neurons, called place cells, serve as the brain’s GPS system to track location. In red is hippocampal zone CA2. The blue area shows the transmission sites of nerve signals between neurons in the neighbouring CA3 zone and dentate gyrus, part of the hippocampus involved in episodic memories. Credit: Raunak Basu, University of Utah, Salt Lake City. Source: NIH image gallery, Flickr. Related Open Biology article “Development of the Mammalian Cortical Hem and its derivatives: the Choroid Plexus, Cajal-Retzius Cells, and Hippocampus” by Samantha Moore and Angelo Iulianella doi:10.1098/rsob.210042