Insect olfaction: a map of smell in the brain

Humans use three classes of photoreceptor to span the visible spectrum, but smell relies on hundreds of distinct classes of olfactory receptor neuron. Even the simple fruitfly has around 50 classes of olfactory receptor neuron. Two new studies map the projections of the great majority of these neurons into stereotyped positions in the fly brain, giving us an almost complete atlas of olfactory information transfer.