This book was initiated as lecture notes to a course in biological physics at Copenhagen University in 1998–1999. In this connection, Chapters 1–5 were developed as a collaboration between Kim Sneppen and Giovanni Zocchi. Later chapters were developed by Kim Sneppen in connection to courses taught at the Norwegian University of Science and Technology at Trondheim (2001) and at Nordita and the Niels Bohr Institute in 2002 and 2003.

A book like this very much relies on feedback from students and collaborators. Particular thanks go to Jacob Bock Axelsen, Audun Bakk, Tom Kristian Bardøl, Jesper Borg, Petter Holme, Alexandru Nicolaeu, Martin Rosvall, Karin Stibius, Guido Tiana and Ala Trusina. In addition, much of the content of the book is the result of collaborations that have been published previously in scientific journals. Thus we would very much like to thank:

• Jesper Borg, Mogens Høgh Jensen and Guido Tiana for collaborations on polymer collapse modeling;

• Terry Hwa, E. Marinari and Lee-han Tang for collaborations on DNA melting;

• Audun Bakk, Jacob Bock, Poul Dommersness, Alex Hansen and Mogens Høgh Jensen for collaborations on protein folding models and models of discrete ratchets;

• Deborah Kuchnir Fygenson and Albert Libchaber for collaborations on nucleation of microtubules and inspiration;

• Erik Aurell, Kristoffer Bæk, Stanley Brown, Harwey Eisen and Sine Svenningsen for collaborations on λ-phage modeling and experiments;

• Ian Dodd, Barry Egan and Keith Shearwin for collaborations on modeling the 186 phage;

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