All forms of life display a remarkable variety of active processes on different length scales. We develop biophysical descriptions to understand how these active processes mediate the flow of energy and matter to self-organize cellular order and function. These descriptions span a wide range of length scales, from structure-function relations of molecular-motor heads, up to the cellular activity of hearing organs. We believe that a mutual stimulation of theoretical considerations and experimental findings is a beautiful way to decipher nature's fundamental principles.