Environmental pollution of mercury (Hg) is a broad concern due to the propensity of this metal to biomagnify in aquatic food webs. The methylated form of the metal, monomethylmercury, bioaccumulates in organisms and is a potent toxin for humans and wildlife. Therefore, the management of contaminated ecosystems typically aims to minimize the distribution of Hg (both organic and inorganic forms) to waterways and especially to areas vulnerable to the production of methylmercury by anaerobic bacteria. Our group and others in the scientific community have made significant advances in recent years in understanding the processes contributing to the production of methylmercury in the environment. These contributions include a new understanding of the nanoscale processes controlling the geochemical forms of Hg in soil and sediments and the microbial processes that underpin the production methylmercury. This talk will provide an overview of these findings and present new strategies to quantify the bioavailability and methylation potential of Hg in sediments.