A new package of papers examines the largest map yet of mammalian brain tissue. The cubic millimeter worth of brain tissue represents the largest piece of a brain we’ve ever understood to this degree, and the researchers behind this project say that the mouse brain is similar enough to the human brain that they can even extrapolate things about us. A cubic millimeter sounds tiny—to us, it is tiny—but a map of 200,000 brain cells represents just over a quarter of a percent of the mouse brain. A proportionate sample of the human brain would be 240 million cells. And since even this large mapping of brain tissue is still very incomplete, the number of “like” neurons is likely even higher in reality.