Many areas of science and industry require a fundamental understanding of crystal dissolution. Examples are diverse and include chemical weathering, pharmaceutical delivery, and the response of marine carbonates to CO2 increases. Understanding these processes ultimately demands knowledge of reaction dynamics. Techniques allowing high-resolution observations of dissolving crystals have greatly improved our understanding of reaction kinetics at a variety of scales. Atomic force microscopy and vertical scanning interferometry can reveal reaction mechanisms and permit tests of working hypotheses. However, understanding the substantial complexity and heterogeneous distribution of surface reactivity cannot be made by simple observation alone but requires advances in fundamental theory. Model simulations of molecular-scale processes provide the critical link between nanoscale surface observations of crystal dissolution and the phenomenological result at scales of environmental importance.