V(D)J recombination, less commonly known as somatic recombination, is the unique mechanism of genetic recombination that occurs only in developing lymphocytes during the early stages of T and B cell maturation. The process results in the highly diverse repertoire of antibodies/immunoglobulins (Igs) and T cell receptors (TCRs) found on B cells and T cells, respectively. The process is a defining feature of the adaptive immune system and its development was a key event in the evolution of jawed vertebrates.