CaM-kinases are a family of enzymes enriched in nervous tissue that are activated by binding to calcium-saturated calmodulin. Each CaM-kinase has unique properties, but all catalyze the transfer of a phosphate group from ATP to a Ser or Thr residue in substrate proteins. In some cases, the kinases are themselves substrates for phosphorylation, and phosphorylation alters their activity. These phosphorylation events are found to regulate almost every biological process in cells and are essential for tuning the cellular response to environmental stimuli over timeframes ranging from seconds to days.