English: Complete cell lineage of C. elegans.

The history of cellular divisions that sequentially tracks the parents of a particular cell up to its original ancestor, the zygote cell, is called cell lineage. Simple organisms such as the C. elegans worm tend to have a deterministic cell lineage, meaning that for any given embryo, the cells divide following exactly the same pattern. More complex organisms tend to have a deterministic lineage only in the early stages of embryogenesis and then, as large numbers of cells of similar type are required, they tend to generate these cells by following non-deterministic, although likely sterotypic, patterns.

Studying the cell lineage of an organism is important because it helps in the understanding of how a particular cell defines its fate in the organism. It also helps to understand how mutations and environmental factors may perturb the embryogenesis process and result in malformed organisms. In the context of studying gene functionality, the cell lineage also provides a baseline layer upon which the behavior of genes can be laid out across space and time as the organism develops.