Rapid advances have been made in recent years in understanding the genetic makeup of mankind. The human genome project has identified approximately 32,000 genes that occur in humans. It is now possible to perform genetic profiling with many of the genes to understand embryogenesis, growth and development, the normal state, senescence, diseases, and tumorogenesis. Techniques in molecular diagnostics are becoming available that will expand the ability to provide more precise diagnoses, predict response to treatment, evaluate treatment, and predict prognosis and outcome. Genetic profiling will, in the future, direct therapy by providing specific targets for development of medications, antibodies, and gene therapy. More recently, the attention of the scientific community has turned toward the gene products within the cell and tissue matrix, namely proteins. The field of proteomics is an evolving area, which may shed light on the proteins associated with diseases and tumors. This will again provide a mechanism for creating personalized, designer therapies for individual patients or groups of patients with similar diseases based on expression profiling. The final avenue of exploration in understanding cell function is the metabolites that occur as the end products of cellular function (metabolome). These metabolites, or improper degradation of cellular proteins, may lead to disease and neoplasia. The role of the pathologist in expression profiling for diseases and tumorigenesis is of considerable importance in providing diagnostic information and predicting outcome based on pathobiologic features of diseases and tumors.