One of the most remarkable features of the brain is its capacity to form and store memories. Decades of research have revealed that memories are stored as changes in the strength and number of connections that form between neurons. While the overall structure of the nervous system is genetically hardwired, neural circuits undergo extensive sculpting and rewiring in response to a variety of stimuli. This process of experience-dependent changes in synaptic connectivity is called synaptic plasticity. By modifying brain wiring in response to experiences, synaptic plasticity provides a biological means of integrating nature and nurture to determine our identities.