Proposed research will develop a new quantitative optical microscopy technique providing high resolution, high accuracy, phase, amplitude and polarization images of transparent, unstained, biological specimens. In conjunction with existing methods of quantitative fluorescence microscopy and enabled by its direct and complete access to a target's physical and chemical/molecular information, it will lead to fully digital/computational, comprehensive, multi-modal optical microscopy of biological specimens and significantly advance the capabilities of current optical methods. The new microscope will be built by coupling a novel (demonstrated) optical phase, amplitude and polarization sensor to a modern commercially available microscope chassis. The sensor will be calibrated using a combination of standard techniques (e.g. integrating sphere), extensions of specific techniques used in preliminary work, and custom phase microscopy targets. Imaging performance will be tested on a carefully chosen representative set of transparent specimens. The chosen imaging targets will provide different optical microscopy challenges that are important both for the engineering development and for gaining insight into new ways of solving important biological problems: various monolayer cultured cells, thin mouse tissue samples, and C. elegans worms at different stages of development. Significant improvements to current optical phase microscopy, as enabled by the proposed method, will include: a) imaging (without staining) low contrast organelles, invisible by existing phase contrast or DIC microscopy (e.g. Golgi apparatus);b) vastly more powerful digital processing through consistent application of linear processing algorithms (the data is linear in object information) to quantitative multi-modal imaging data to provide entirely new information/views;and c) true 3D volume information of transparent, unstained, specimens by using the quantitative phase data in diffraction tomography or z-stack reconstruction algorithms. Such improvements will enable, for example, more advanced optical microscopy for high- throughput genetic screening, faster, more accurate (quantitative) automated histology of transparent, unstained, tissue samples, and complex genetic databases containing comprehensive, fully digital, quantitative multi-modal optical microscopy data on specific phenotypes. This research will develop a new quantitative optical microscopy technique capable of providing essential new information to biologists, in a manner amenable to wide use. By providing complete access to the physical/chemical properties of biological specimens, it will enable the application of advanced computer processing techniques to obtain and store (digitally) new information relevant for both basic and clinical research.