Advances in DNA sequencing and synthesis technologies concurrent with the development of new recombinant DNA approaches have enabled the extension of directed evolution algorithms to the genome-scale. It is now possible to simultaneously map the effect of mutation(s) in each and every gene in the genome onto almost any screenable or selectable phenotype in less than a week. Such maps can be used to direct the design and construction of libraries containing billions of rationally designed combinatorial mutations. Such combinatorial libraries can now also be created and evaluated in less than a week. The review presents and discusses these new technologies within the context of directed evolution and inverse metabolic engineering.