Implicit and explicit memory both have a short-term component lasting minutes (for example, remembering the telephone number you just looked up) and a long-term component that lasts days, weeks, or a lifetime (for example, remembering your mother's birthday). For both memory processes, the conversion from short- to long-term memory generally requires repetition. And in both, long-term memory requires the synthesis of new proteins. Short-term memory is mediated by modifications of existing proteins, leading to temporary changes in the strength of communication between nerve cells. In contrast, long-term memory involves alterations of gene expression, synthesis of new proteins, and growth of new synaptic connections. It is the growth of synaptic connections—they may be forming in your brain as you read this—that produces enduring long-term memory. Insights into the molecular biology of memory storage have led to an improved understanding of memory disorders produced by brain diseases such as Alzheimer's—and the promise of improved treatments.