Developing brains constantly sprout new neuronal connections called synapses as they learn and remember. Important connections -- the ones that are repeatedly introduced, such as how to avoid danger -- are nurtured and reinforced, while connections deemed unnecessary are pruned away. Adult brains undergo similar pruning, but it was unclear how or why synapses in the adult brain get eliminated. Now, a team of researchers has found the mechanism underlying plasticity and, potentially, neurological disorders in adult brains.