Numerous human (and animal) diseases are the consequence of unwanted pathological crystallization, from arthritis to gout to kidney stones to (surprisingly) malaria. Better understanding of these diseases and the design of therapies demand a fundamental understanding of crystal growth - a mainstay of materials science - and the fate of crystals in vivo. Consequently, there is an underappreciated role for materials science, particularly solid-state chemistry, and the deployment of materials science concepts in identifying solutions to this class of diseases. This presentation will highlight diseases stemming from pathological crystallization and the use of methods and tools generally available to the materials scientist for unraveling the critical steps responsible as well as new therapeutic approaches. For example, atomic force microscopy can provide considerable insight, at the near molecular level, into crystallization events under growth conditions, the role of crystal growth inhibitors, and the adhesion properties of crystal surfaces, which is critical to the aggregation of crystals in vivo. Specific examples will include crystalline materials responsible for kidney stones, including calcium oxalates and L-cystine. Studies of L-cystine crystallization have produced promising drug candidates, exemplifying translational research in which physical science can impact human health.