Drug discovery is the process by which potential new medicines are identified. Drugs have a positive impact on a disease by binding to target molecules in the body and changing their functions. Discovering novel drug-like molecules starts with either a target-based or phenotype-based approach. In a target-based approach, one theorizes, based on basic research data, that a drug that binds and interferes with the function of a particular protein should help a disease. After a target is identified, then a drug-like molecule is identified that binds to it and alters its function in the desired way. In phenotypic drug discovery, drug-like molecules are discovered that have a positive impact on a disease model system, like the function or health of human cells in culture.