Biotechnology is the marriage of engineering and technology principles to the biological sciences. Common applications include the development of new microorganisms or biological substances for industrial applications. These can include hormone production, waste cleanup, bioconversion of organic wastes, genetic engineering of new organisms, drug manufacturing and so forth.
Biotechnology does not necessarily use living organisms. For example, it can focus on DNA chips in genetic research, or radioactive medical tracers. It can even use active cells from living organisms -- but not the organism itself -- such as when human lymphocytes are used in vaccine development.
Among the most exciting of biotech fields is the engineering of new microorganisms, with the goal of producing insulin or antibiotics cheaply and efficiently. Other applications include the development of transgenic plants and animals, in which foreign genes are introduced externally, so as to produce enhanced organisms (e.g. cows that produce extraordinary quantities of milk).