Microorganisms produce and excrete a versatile array of metabolites with different physico-chemical properties and biological activities. However, the ability of microorganisms to release volatile compounds has only attracted research attention in the past decade. Recent research has revealed that microbial volatiles are chemically very diverse and have important roles in distant interactions and communication. Microbial volatiles can diffuse fast in both gas and water phases, and thus can mediate swift chemical interactions. As well as constitutively emitted volatiles, microorganisms can emit induced volatiles that are triggered by biological interactions or environmental cues. In this Review, we highlight recent discoveries concerning microbial volatile compounds and their roles in intra-kingdom microbial interactions and inter-kingdom interactions with plants and insects. Furthermore, we indicate the potential biotechnological applications of microbial volatiles and discuss challenges and perspectives in this emerging research field.