Decoding the essence of being — understanding the brain and all its connections, that is Connectomics. Scientists have now made an important step in this direction: After analyzing data for four years, aided by about 200 undergraduate students, the scientists created a precise diagram of all nerve cells and their connections in a piece of mouse retina. Although representing only a small fraction of the brain, this diagram already revealed a new cell type and circuit motifs that may help to understand the reactions of certain retinal cells.