The nucleus of a human cell contains between 30 000 and 40 000 genes. This complete set is called the human genome. The Human Genome Project (HGP) is an international 13-year research project formally begun in October 1990 to break the code of human DNA. The project was planned to last 15 years, but rapid technological advances accelerated the completion to 2003. Project goals were to determine the complete sequence of the 3 billion DNA subunits (bases), identify all human genes, and make them accessible for further biological study.