Interaction of light with matter depends on the properties of a studied material and the wavelength of light used in our experiments. If we aim at determining optical properties of a material in a specific region of the electromagnetic spectrum, we perform spectroscopy. Our instrumentation background can cover a wide range of wavelengths from terahertz to near-ultraviolet. One of the key pillars of our research activity is focus on characterization of the complex polarization properties of materials using ellipsometry. Our laboratory boasts, among others, unique time-domain terahertz spectroscopy. Unlike common optical methods, it allows not only radiation intensity but also its phase, i.e. full optical response, to be detected. The latest newcomer in our laboratory is a prototype of the Mueller matrix microscope, which is a combination of a conventional optical microscope and spectroscopic ellipsometer. It is exactly this combination that gives the study of polarization properties a brand new dimension.