I propose to develop and apply a novel approach to optical microscopy to enable the direct visualization and study of dynamics on the nanoscale in biological and condensed matter physics. Given the speed with which nanoscopic objects move at ambient condition, this requires simultaneously very fast (ms) and precise (nm) imaging. The challenge is to avoid excessive perturbation of the system and enable imaging in biologically compatible environments without compromising imaging performance by pushing interferometric scattering to its theoretical limits.Using these advanced capabilities, I will study the dynamics and thereby the structure-function relationships in three fundamental systems that are currently not captured by even the most advanced biophysical approaches. These include: (1) the flexibility of DNA on short length scales, (2) diffusion in artificial and cellular membranes and (3) the three-dimensional power stroke of molecular motors such as myosin and kinesin.Fundamentally, this work aims to develop and establish a high-speed, non-invasive camera on the nanoscale that will enable us to study and eventually understand nanoscopic motion, dynamics and potentials on the relevant, rather than currently achievable, size and time scales.