The Earth Microbiome Project has published its first comprehensive overview of global microbial diversity. The project received 27,751 samples, which originated from 43 countries and covered diverse environments ranging from ocean sediments to plant pollen. Thompson et al. isolated, amplified and sequenced 16S rRNA genes in a highly standardized way. To analyse bacterial and archaeal diversity, they used a reference-free approach that did not group sequences according to their similarity to operational taxonomic units. This has the advantage that the results are unbiased by the coverage of existing reference databases. Indeed, only ∼10% of their sequences matched existing 16S rRNA databases, and the remaining sequences represent novel microbial diversity. Both the protocols and the data are a tremendous resource for future research.