The Leica TL4000 RC base with Rottermann Contrast™ technique, a relief illumination technology, shows the changes of the refractive index as differences in brightness and provides ideal lighting conditions for observation and imaging with any high performance Leica Stereo Microscope, especially at high magnification. The unique technology allows a substantial increase in contrast of barely visible structures in positive (appear elevated) or negative (appear as depressions) relief for many molecularor developmental biology applications. Adjustable mirror with planar and concave mirror position provides dynamic relief contrast, which allows users to toggle quickly between positive and negative effects and easily distinguish between similar structures.