Various stimuli produce different changes in cell, tissue and organs. Some of these changes are adaptive or accommodative for the cell. These changes are called adaptive changes and include hypertrophy, hyperplasia, metaplasia and atrophy. Also included dysplasia although, it is not an adaptive response but very important as mild and moderate form is reversible, but severe dysplasia is irreversible and termed as carcinoma in situ. In adaptive changes, the cell adapts to a new environment but retains its capacity as a normal cell. Once this adaptive capacity is stretched beyond normal, the cell goes to reversible or irreversible cell injury or cell death.