Programmed cell-death (or PCD) is the death of a cell in any form, mediated by an intracellular program. PCD is carried out in a regulated process, which usually confers advantage during an organism's life-cycle. For example, the differentiation of fingers and toes in a developing human embryo occurs because cells between the fingers apoptose; the result is that the digits are separate. PCD serves fundamental functions during both plant and multicellular animal tissue development. Apoptosis and autophagy are both forms of programmed cell death, but necrosis was long seen as a non-physiological process that occurs as a result of infection or injury.