A review. This review describes a concept aimed at rational and maximal structure proliferation. To this end, simple arom. or heterocyclic starting materials, often bulk chems., are converted into all regioisomerically possible polar organometallic intermediates (mostly lithiated species), which then may be combined with any of the countless electrophiles to provide attractive new building particularly functionalized derivs. The practical implementation relies on a set (\"toolbox\") of sophisticated recipes developed by mechanistically guided modification of the two most prominent exchange methods used for the generation of polar organometallic compds.: hydrogen-metal and halogen-metal interconversion. These mutant methods (\"old methods in a new outfit\") amplify the existing options for org. synthesis by ensuring max. regioflexibility. At the same time they offer new insight into factors that govern organometallic reactivity and provide hints on how to alter or fine tune this reactivity judiciously. [on SciFinder (R)]