While most current biological research focuses on molecular, biochemical aspects of cell processes, we are interested in the physical properties of cells and tissues, and their importance for biological function. Many physiological and pathological changes of cells involve a restructuring of the cytoskeleton, and corresponding changes in their mechanical fingerprint. We are exploiting cell deformability as a sensitive marker of such functional changes using an optical stretcher and a novel, high-throughput microfluidic technique. Our findings suggest the use of cell compliance to monitor physiological processes, such as differentiation or cell division, as well as diagnosing pathologies, including cancer or infections. Beyond individual cells, also the mechanical properties of biological tissues are increasingly being recognized as important as cells measure and respond to the mechanics of their environment. We are investigating the mechanosensitivity of neurons and glial cells in the context of development and pathologies of the central nervous system. This research could lead to novel therapeutic approaches in traumatic injuries to the CNS and neurodegenerative disorders.