This talk will focus on the significant progress made in the field of UV-Vis-NIR spectrophotometry over the last 25 years, leading up to the current state-of-the-art tools in material characterization of advanced optical materials. We will have in-depth discussion on the properties of the light beam and sample spot of UV-Vis-NIR Spectrophotometer, and the use of Integrating spheres for scattering measurements. Additionally, we will also analyze a multitude of challenging optical measurement problems and the corresponding solutions for accurate measurements of diffuse and textured samples. Furthermore, we will also discuss the effect of light polarization, angular accuracy, beam-shift and inter-reflections on variable angle spectroscopy, which is applied in optical thin film analysis and scattering measurements. Understanding these effects have resulted in state-of-the art tools for these measurements.