The first two editions of Molecular biology, published in 1983 and 1987, were written by that splendid author, David Freifelder. Unfortunately he is no longer alive to chronicle the advances in the discipline. The writing of this edition, with its slightly modified title, was the responsibility of a new author, who obviously had a lot to live up to. Much has happened in molecular biology and in the storing, accessing, and presentation of biological information since 1987. This has necessitated a complete revision of the earlier edition(s). However, the text is still designed to introduce molecular and genetic aspects of the biology of cells to undergraduate and first-year graduate students: a very difficult task by anybody's standards.