In the last forty years, differential-interference-contrast (DIC) microscopy has gained popularity in biomedical research as an effective optical microscopy technique used to observe unstained transparent specimens under a transmitted-light configuration. The DIC image formation is caused by the interference of two orthogonally polarized beams, which are laterally split of a few tenths of a micrometer by a Wollaston prism, phase shifted when passing through different materials across the specimen and then successively recombined by a sliding prism. The resulting image has a three dimensional, high contrast appearance, which can be enhanced by adjusting the sliding prism along the direction of the split in order to introduce a uniform phase difference between the two beams.