It is becoming increasingly recognised that soil microbial communities perform important ecological roles in terrestrial ecosystems. As a consequence, there is a growing demand for knowledge on the factors that regulate the development and diversity of microbial communities in terrestrial ecosystems. In this talk, I will discuss recent advances in our understanding of how soil microbial communities develop across successional timescales, ranging from tens to millions of years, and provide insights into the factors that regulate these patterns. First, I will draw on recent studies of chronosequences in the European Alps that show how heterotrophic microbial communities develop during initial stages of succession and how they function in the absence of substantial carbon inputs from autotrophs. I will also illustrate how microbial communities develop, and how patterns of microbial carbon utilisation change, as succession proceeds and autotroph-derived organic matter accumulates in soil. Second, I will examine data from a comparative study of long-term chronosequences across the globe, with different aged geological substrates. This study revealed distinct, and often consistent, patterns of soil microbial community development (biomass, composition and diversity) and function (decomposition) that were related to changes in resource availability and quality, and plant productivity. Results from this study provide insights into factors that regulate microbial community structure over long-timescales of thousands to millions of years. They also provide evidence for distinct and relatively consistent associations between the producer and belowground microbial subsystems over long timescales. Ultimately, a key aim of this talk will be to illustrate the value of the chronsequence approach as a model for studying patterns and mechanisms of soil microbial community development in terrestrial ecosystems.