Where do our memories get stored and how are they retrieved again?
Long-term potentiation (LTP) is thought to be a major mechanism of long-term learning, in which neurons throughout the brain undergo permanent physiological changes (e.g., migration of AMPA receptors to neuronal terminal buttons) that allow maintenance of the memory trace. A simpler version of this would be the famous aphorism (and oversimplication) regarding Hebbian learning -- "cells that fire together wire together."