This book is the result of outstanding collaborations with inspiring collegues and friends. A part of its content is based on an earlier book that I published with Giovanni Zocchi, with whom Mogens H. Jensen and I started the biological physics initiative at Copenhagen University. The major content of the book has been developed during the last decade, when I had the luck to be in charge of the Center for Models of Life at the Niels Bohr Institute. This center exists thanks to generous funding from the Danish National Research Council, who gave me the option to invite and employ inspiring collaborators.

Much of the content of this book is based on activities at the center. The book was also developed in parallel with our scientific endeavors and bachelor degree level courses on gene regulation, networks and complex systems for which I had the pleasure of lecturing. Accordingly, the big part of the book is devoted to classical models from molecular biology, spanning a wide spectrum of model systems and synthetic circuits as they unfold in classical model organisms like Escherichia coli.

I would hope that this book is useful for bachelor degree-level students in any quantitative discipline related to physics or biology. In fact, I believe the book also could be of inspiration for mathematically inclined high school and college students.