This chapter serves as an introduction to the major types of microscopy that are applied to the characterization of lignocellulosic biomasses. The covered techniques include optical microscopies (light, Raman, and confocal microscopy), scanning probe microscopy, and electron microscopy. This chapter provides a general description of the principles, advantages and drawbacks, type of information that can be obtained using the different microscopic techniques and includes a wide range of examples on the use of such techniques to characterize lignocellulosic biomass samples before and after pretreatments. Finally, some of the reviewed microscopic techniques were used to visualize samples of wheat straw nodes before and after acid and alkali pretreatments. This chapter is designed to help scientists select the best microscopic technique to study biomass feedstocks with recalcitrant natures.