Metabolomics: Pandora's Box or Aladdin's Cave?

Functional genomics, the elucidation of gene function from studies of the effects of gene modification on cellular phenotype, has prompted the development of massively parallel and increasingly comprehensive screening tools for assessing the expression of mRNAs (transcriptomics) and proteins (proteomics). For a more complete description of the effects of changes in genotype or physiological conditions on cellular phenotype, we also need to define the status of a third class of biomolecules in the cell, the small-molecule metabolites. Study of the latter has been termed metabolomics and the metabolite complement the metabolome.