In absorbing, anisotropic objects the refractive index and the absorption vary with direction. As with double refraction (birefringence), there are two main directions of anisotropy, which are perpendicular to each other. This phenomenon is called dichroism and may be studied in the polarizing microscope with one polarizer. By rotating the microscope stage the object is brought in different directions to the vibration plane of the polarized light, and the change of light absorption is observed. Study of dichroism allows conclusions as to the submicroscopic fine structure of cells.