Biology lab stain is a process used to identify and differentiate between different types of cells, bacteria, and other microorganisms. Eosin is a red dye used to stain tissue sections in order to make them visible under a microscope. AGAR is a gelatinous substance used as a culture medium for growing bacteria and other microorganisms. GELS are a type of matrix used to separate molecules based on size and charge. Ameba and AMOEBA are both single-celled organisms that can be studied using the staining process.