My research primarily focusses on developing methods for building ligand models into the electron density derived from x-ray crystallography screening experiments. Screening experiments are used to probe the chemistry of a binding site of a protein, by determining the bound structure of fragments with affinity for the binding site. The bound structures of the highest affinity fragments from these experiments guide the development of a therapeutic drug. However, the attrition rate of the drug design process remains high, and we propose that additional information from fragment-screening experiments could help improve the reliability of the process.