A review is given of Frőhlich's approach to biology from the side of theoretical physics, and illustrated in the context of his prediction of three types of coherent excitations in living systems based on their dielectric and elastic properties and far-from-equilibrium (non-linear) character. Supporting experimental evidence is presented, and the difficulty in achieving reproducibility addressed. His envisaged role of coherent excitations in cell division and its control is outlined, together with the implications for cancer - as understood at the time of his work.