One of the most important trends of physics research that emerges at the turn of the century is physical approach to biology. Biology will provide novel materials, even revolutionary paradigms for physics at large. On the other hand, physics, if properly extended to biological systems, will give basic and quantitative understanding of complex biological processes, as well as diverse biomaterial and biotechnological applications. First, I will talk about the natures of biological systems in nanoscales and relevant statistical physics description, then describe how the nature utilizes the diverse fluctuations that abound in biological systems to bring about a self-organization, exemplifying membrane fusion. A cooperative coupling of shape and charge fluctuations on two interacting membranes induces a dynamic instability to spontaneous growth of in-phase surface undulation at a wavelength, thereby by reducing the energy barrier to fusion.