In the preface to previous editions of our book we set ourselves the task of producing an undergraduate text that covered the theoretical principles and practical details of the experimental techniques that are basic to an understanding of, and that support advances in, biochemistry. In the 30 years that have elapsed since the first edition was launched in 1975, there have been dramatic advances in our understanding of the biochemical processes that characterise living cells. Such advances are typified by the recent completion of the Human Genome Project and the emergence of numerous allied fields of study such as bioinformatics and proteomics. The new generic discipline of molecular biology embraces many of these areas of research and so we have felt it appropriate to broaden the title of the book to include molecular biology, as it clearly falls within our original objective. In the process of taking a decision on the content of this sixth edition of our book, we have also attempted to respond to the extremely constructive and encouraging feedback we have received to the survey we conducted of the many academic departments in UK and overseas universities and other institutions that routinely use our book and recommend it to their students. The outcome is that we have broadened the topics covered within the book by including two new chapters, one on cell culture, the other on microscopy.