This book is dedicated to the multiple aspects, that is, biological, physical and computational of DNA and RNA molecules. These molecules, central to vital processes, have been experimentally studied by molecular biologists for five decades since the discovery of the structure of DNA by Watson and Crick in 1953. Recent progresses (e.g. use of DNA chips, manipulations at the single molecule level, availability of huge genomic databases...) have revealed an imperious need for theoretical modelling. Further progresses will clearly not be possible without an integrated understanding of all DNA...