Biomedical tissue engineering is a biomedical engineering discipline integrating biology with engineering to create tissues or cellular products outside the body or to make use of gained knowledge to better manage the repair of tissues within the body. This discipline requires understanding of diverse biological fields, including cell and molecular biology, physiology and systems integration, stem cell proliferation and differentiation with lineage attributes, extracellular matrix chemistry and compounds, and endocrinology. It also requires knowledge of many engineering fields, including biochemical and mechanical engineering, polymer sciences, bioreactor design and application, mass transfer analysis of gas and liquid metabolites, and biomaterials.