Evolutionary engineering is an interesting scientic endeavor blending aspects of biological evolution and directed manipulation. In its application to metabolic engineering, this combination seeks to make use of what a cell inherently knows how to do (grow and evolve) and directs human intervention to achieve some metabolic engineering goal. roughout this chapter the term “cellular objective” will be used to generically describe the functional purposes inherent in a cell. is is contrasted with a “metabolic engineering objective” that describes the function that we as engineers would like to introduce or improve in a cell.