 The larval mushroom body, MB, consists of two distinct lobes, each containing a set of neurons that are responsible for processing sensory inputs and controlling motor outputs. In the larvae, these neurons are generated by a single type of neuron called the gamma neuron. During metamorphosis, the larval MB undergoes significant changes, including the death of some neurons and the trans-differentiation of others. This process results in the formation of the adult MB, which contains 16 distinct compartments. Each compartment is composed of a unique set of neurons, which are derived from either the larval gamma neurons or newly formed neurons. The adult MB is able to process sensory inputs and control motor outputs, but it does not retain any memories from the larval stage. Instead, the adult MB is a completely new structure, built up from the larval MB and the newly created neurons. This article was authored by James W. Truman, Jacqueline Price, Rosa Elmiaris, and others.