Multicellular organisms are composed of groups of different cell types. The importance in the evolution of cellular diversity of regulatory changes in genes that control cell specification has been revealed by a recent study of developmental genes in Arabidopsis.
Dolan, L. (2001, September 4). Plant development: The benefits of a change of scene. Current Biology. Cell Press. https://doi.org/10.1016/S0960-9822(01)00413-4