Surface technologies based upon selection of ligands from combinatorial libraries herald a revolution in molecular research and drug discovery. Molecular diversity is generated by random combinations of monomeric building blocks to form polymeric conformers that constitute 'shape libraries'. The media for exploring surfaces of target molecules include synthetic or biological polymers consisting of natural or modified amino acids, nucleotides, carbohydrates and other organic materials. Targets can be any biological surface, including enzymes, antibodies, receptors and other regulatory molecules. The power of combinatorial selection is in finding conceptual leads for designing high-affinity ligands and effector molecules for the analysis and manipulation of biochemical interactions.