Microbes similar as plants can produce a plethora of “smells”, that are volatile organic compounds. Microbes could use those “smells” to interact and talk over distance in soil. However, our knowledge on the importance of those “smelly” (volatile-mediated) conversations for the belowground ecosystem functioning is still limited. Within in this thesis, novel aspects on the ecological role of volatiles in microbial interactions belowground were studied. It was revealed that the mix and biological activity of microbial volatiles released in soil is strongly dependent on who is there and interacting with whom. Moreover, it was demonstrated that volatiles can represent important long-distance messengers for soil microbes such as information about suitable food sources or, in case of bacteria-protist-interactions, about suitable prey. On the other hand, plants release volatiles in to soil that can attract beneficial bacteria. Overall, findings in this thesis contribute to our knowledge on the importance of volatile-mediated (“smelly”) communication in ecosystem functioning belowground.