Nanoscale materials, both inorganic and organic, are ubiquitous in the environment. Recent investigations into the nanoscale chemistry and mineralogy of toxic metal distribution in nature have revealed novel and unexpected insights. Additionally, corresponding advances in the field of nanoscience have demonstrated that the physical properties and reactivity of nanomaterials vary dramatically as a function of material size. Geoscientists are uncovering a fascinating story of how the immense surface area, unusual properties, and widespread distribution of natural nanomaterials often affect the fate of toxic metals in surprising ways.