Pt. I. Mysteries, metaphors, models. What the ancients knew ; What's inside cells -- Pt. II. Diffusion, dissipation, drive. The molecular dance ; Random walks, friction, and diffusion ; Life in the slow lane: the low Reynolds-number world ; Entropy, temperature, and free energy ; Entropic forces at work ; Chemical forces and self-assembly -- Pt. III. Molecules, machines, mechanisms. Cooperative transitions in macromolecules ; Enzymes and molecular machines ; Machines in membranes ; Nerve impulses ; Epilogue -- Appendix A. Global list of symbols and units -- Appendix B. Numerical values -- Appendix C. Additional problems.