This book was written, to a not inconsiderable degree, on the basis of the course "The Problems of Modern Biophysics" which the author gives to the students and postgraduates of the Biophysical Department at Moscow University School of Physics. It is meant for those who have a sufficiently good background in physics as well as in biology. I have tried to make this book intelligible to a broader circle of readers, i.e., to physicists not competent enough in biology, and to biologists not competent enough in physics. I hope that I have succeeded. This book is neither a textbook nor a systematic account of a field of science. I think that in modern biological physics, i.e., in the branch of biology where people having fundamental physical or physico-chemical education are working, so many specific answers have been recently obtained that it is now just the right time to ask at least several questions of a general nature. The aim of this book is to formulate such questions though their choice is, to a considerable degree, determined by the authors preferences and interests.