Apoptosis ( /ˌæpəˈtoʊsɪs/) is the process of programmed cell death (PCD) that may occur in multicellular organisms.Biochemical events lead to characteristic cell changes (morphology) and death. These changes include blebbing, cell shrinkage, nuclear fragmentation, chromatin condensation, and chromosomal DNA fragmentation. (See also apoptotic DNA fragmentation.)

In contrast to necrosis, which is a form of traumatic cell death that results from acute cellular injury, apoptosis, in general, confers advantages 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. Unlike necrosis, apoptosis produces cell fragments called apoptotic bodies that phagocytic cells are able to engulf and quickly remove before the contents of the cell can spill out onto surrounding cells and cause damage.

Between 50 and 70 billion cells die each day due to apoptosis in the average human adult. For an average child between the ages of 8 and 14, approximately 20 billion to 30 billion cells die a day.

Xiaodong Wang (simplified Chinese: 王晓东; traditional Chinese: 王曉東; pinyin: Wāng Xiǎodōng, born 1963) is an American biochemist best known for his work with cytochrome c. His laboratory developed an in-vitro assay for the activation of the apoptosis related proteinase Caspase-3. This allowed the biochemical purification a complex of Cytochrome c, Caspase-9 and the Apoptotic Protease Activating factor-1 (Apaf-1). These components are essential for forming a ternary complex called the apoptosome that activates Caspase-3 downstream of the intracellular or mitochondrial pathway of apoptosis.

He was awarded the 2006 Shaw Prize in Life Science and Medicine.

Wang is a member of United States National Academy of Sciences and the Howard Hughes Medical Institute. Currently he is a professor at National Institute of Biological Sciences, Beijing.