The metabolome represents the collection of all metabolites in a biological organism, which are the end products of its gene expression. Thus, metabolic profiling can give an instantaneous 'snapshot' of the physiology of that cell.
Sort of like analyzing how well you car is running by hooking a gadget up to the exhaust pipe and measuring the degree of partially combusted by-products.
Since the metabolome is closely tied to the genotype of an organism, its physiology and its environment (what the organism eats or breathes), metabolomics offers a unique opportunity to look at genotype-phenotype as well as genotype-envirotype relationships. It is estimated that only a quarter to half of endogenous human metabolites in blood or urine have been positively identified.
In general a metabolome in a given body fluid is influenced by endogenous factors such as age, sex, body composition and genetics as well as underlying pathologies. The large bowel microflora are also a very significant potential confounder of metabolic profiles and could be classified as either an endogenous or exogenous factor. The main exogenous factors are diet and drugs. Diet can then be broken down to nutrients and non- nutrients. Metabolomics is one means to determine a biological endpoint, or metabolic fingerprint, which reflects the balance of all these forces on an individual's metabolism.
Metabolic biochemists have arguably been 'doing metabolomics' for decades. It has been suggested that the concept of metabolomics is foreshadowed by Linus Pauling's work toward "orthomolecular medicine" and his hypotheses regarding the predictive capacity of chromatographic profiling of bodily fluids for detection and diagnosis of human disease.