Cell lines are a type of biological entity that is derived from a single cell, which then undergoes multiple divisions to produce a population of cells. These cells can be taken from an organism and grown in a laboratory setting where they continue to divide and multiply. Cell lines are used extensively in research as well as for producing therapeutic products such as vaccines or biological drugs. They provide a consistent source of cells that can be genetically identical, allowing scientists to study the effects of specific genetic changes on cellular function. Some common examples of cell lines include HeLa (derived from a woman with cervical cancer), Chinese hamster ovary (CHO) cells and mouse myeloma cells.