A learning module for molecular level analysis of protein structure and ligand/drug interaction through the visualization of X-ray diffraction is presented. Using DeepView as molecular model visualization software, students learn about the general concepts of protein structure. This Biochemistry classroom exercise is designed to be carried out by following the detailed instructions that make software handling straightforward. Students learn about protein structure and gain insight into the molecular level of the interaction of two active compounds with their receptor. (Contains 8 figures.)