Although the term genetic engineering has been in use for at least three decades, and recombinant DNA methods are now mainstays of modern research, most biotechnologists' work with living things has little in common with engineering. One reason is that the tools available for building with biological parts have yet to reach a level of standardization and utility equal to that in other engineering fields. Another has to do with methods and mind-sets in biology, although these, too, can be powerfully influenced by technology.