The OWLS grating coupler sensors can yield the number, size and shape of living cells growing on its surface. The OWLS system allows to quantify the surface area of focal adhesion of living cells, at the surface. The measurement takes place in real time and is noninvasive. Applications include toxicology, stem cell and cancer research. With the addition of electrical field stimulation in EC-OWLS systems, living cell behaviour under electrical field can be studied.