The long-term objectives of this project are to decipher the molecular and fine-structural organization of living cells which are responsible for mitotic chromosome movement and related cell motility. We propose to tackle this problem: through polarization optical and related methods of quantitative light microscopy by which we can follow the state of molecular assemblies and ordered fine structure as they dynamically appear and change, directly in living cells; and by developing the instruments and new methods which make feasible these investigations on living cells in real time, as the cells divide normally or under the influence of altered physical, physiological, or pharmacological conditions. Specifically, we will: (1) extend the application of video imaging and digital processing to improve the microscope resolution, image quality, speed, and capacity to enhance and display selected optical features in the live specimen, under conditions of known image reliability; (2) examine the mechanisms of mitotic and related cell motility primarily in the astral system that draws the female and male pronuclei together after fertilization anticipating their fusion, and in mitotic and meiotic spindles during induced microtubule depolymerization and reassembly; (3) advance the means for modulating selected reactions in targeted local sites within a living cell by the use of a minute, focused spot of light which activates or inactivates a photosensitive compound. Cell division, mitosis, and nuclear migration are fundamental, epochal events in the life of every cell. Without their regular progress, our tissues would lose their ability for normal growth, proper differentiation, or balanced sustenance. The technological contributions arising out of this project should also find timely applications in clinical as well as general and industrial microscopy.