The lethal potential of cancer is due to abnormal cell division and aggressive metastatic activity that turn resting cancer cells into motile structures which spread through an organism, resulting in numerous and often uncontrollably growing subpopulations. It is well known that both cell motility and cell division depend crucially on cell mechanics, namely on actin cortex. The actin cortex consists of a dense biopolymer network, steadily contracted by myosin motors. A key to understanding the abnormal motility and proliferation of cancer cells is the investigation and quantification of the physical properties of the actin cortex. Of special interest is the activity of the acto-myosin network and its interaction with the plasma membrane. This actin-membrane interplay is a major contributor to many physical properties of the whole cell. We propose a systematic study of acto-myosin membrane interactions using biomimetic and living cells in combination with a novel optical method that allows simultaneous manipulation and detection of the cell edge with high spatial and temporal resolution. Our main objectives are: a) to quantify the physics of the actin cortex in biomimetic cells; b) to understand the nonequilibrium statistical mechanics of active acto-myosin networks; c) to study of actin-membrane interactions in the cell cortex and the lamellipodium of living cells. The applicant and the host institute provide complementary skills for this project. The applicant has expertise in advanced optical detection methods, cell motility and stochastic processes, and the host institute will provide the biomimetic actin cortex system, expertise on biomimetics, active systems and biology and the interdisciplinary working environment, including biologists and biochemists, necessary for this project. In this respect both the applicant and the host institution will benefit from the fellowship.