Brains are bewilderingly complicated systems of connections between neurons. Mapping those connections is an important step in understanding how brains work. Scientists have recently completed the most ambitious effort yet to construct such a map: a complete document of every neuron and every connection in the brain of an adult fruit fly.

F RUIT FLIES are smart. For a start—the clue is in the name—they can fly. They can also flirt; fight; form complex, long-term memories of their surroundings; and even warn one another about the presence of unseen dangers, such as parasitic wasps.

The head of a Princeton team that mapped the brain of an adult fruit fly -- a watershed step in understanding the human brain -- explains the feat in a way that belies its complexity. "Just like you wouldn't want to drive to a new place without Google Maps,

Unlocking the complexities of the fruit fly brain is a crucial step toward understanding the human brain. Fruit flies share many genetic similarities with humans, making them a va

Wiring diagram lays out connections between nearly 140,000 neurons and reveals new types of nerve cell. Researchers have mapped nearly 140,000 neurons in the fruit-fly brain. This version shows the 50 largest.

The first wiring diagram of every neuron in an adult brain and the 50 million connections between them has been produced for a fruit fly.