Almost all environmentally relevant reactions in nature or in technical applications that involve minerals are surface or interface reactions; whether it is crystal growth, adsorption reactions, mineral dissolution, redox reactions, or even the growth of crystallites from the melt, the actual reactions always take place at mineral surfaces. This is one reason why I got started: to analyze the atomic and electronic structure, the chemistry and reactivity of mineral surfaces. In addition, over the last 20 years, numerous surface-sensitive techniques have been developed to image and analyze surfaces with up to atomic resolution. Thus, it is possible now to resolve reaction mechanisms step by step without relying too much on hypotheses. Furthermore, we can calculate some of these reactions at a quantum mechanical level. This way, it has become much more satisfying to understand environmental reactions, predict these, or optimize certain reaction types for technological applications or remediation purposes.