K-mers play a critical role in the exploration of metagenomic data. They have been widely used to assign taxonomic attributions to the short genomic fragments characteristic of shotgun (metagenomic) sequencing. These approaches provide an assembly-free method for profiling microbial communities, and have helped elucidate the factors driving microbial community composition across biogeochemical gradients. Advances in sequencing technology are now making it cost-effective to sequence microbial communities at sufficient depths to allow for the assembly of high-quality contigs. This has made it possible to adopt k-mer based approaches to enable reliable binning of contigs originating from a single microbial population within a community. In this session, I will present both an overview of how k-mers can be used to assign taxonomic attributions to short metagenomic reads, and discuss how these approaches have advanced to a point where population genomes can be recovered en masse from even complex microbial communities.