Metabolomics is the logical progression of the study of genes, transcripts and proteins. Nutrients, gut microbial metabolites and other bioactive food constituents interact with the body at system, organ, cellular and molecular levels, and effect the expression of genome at several levels, and subsequently, the production of metabolites. This book presents an overview of nutrigenomics and metabolomics tools, and their perspective in livestock health and production. In addition, this book describes how lists of masses (molecular ions) and mass unit bins of interest are searched within online databases for compound identification, the extra biochemical data required for metabolite confirmation, how data are visualised and what the putative and protein sequences are associated with observed metabolic changes. Moreover, environmental metabolomics is the application of metabolomics to the investigation of both free-living organisms directly obtained from the natural environment or laboratory conditions. This book outlines some of the advances made in areas of plant environmental metabolomics. The applications of microbial metagenomics, the use of genomics techniques to the study of communities of directly in their diverse natural environments, are explored as well. Other chapters examine the abnormalities in metabolism of cancer cells, which could play a strategic role in tumour initiation and behaviour.