Industrial scale production, coupled with unique material properties, underpin rising concerns of nano-scale materials inadvertently impacting the health and function of natural systems. Fullerenes, C60 in particular, have been proposed for a variety of applications and are soon expected to be produced in multi-ton quantities. Understanding how these materials behave in natural matrixes, specifically aqueous systems, is needed for accurate risk assessment and to manage waste disposal practices appropriately. Research presented here addresses outstanding questions and expands upon current knowledge regarding C60 nano-scale aggregation in water (nano-C60). Four areas of focus are: 1.) Aggregate formation, composition, and stability 2.) Reactivity with a dissolved reactant (ozone) 3.) Association with mineral surfaces and 4.) Interaction with selected biological systems. Results indicate that aggregates are crystalline in order and remain as underivatized C60 throughout the formation/stabilization process. The aggregate suspensions readily react with dissolved ozone resulting in a molecularly soluble, highly oxidized fullerene. Furthermore, nano-C60 associates with mineral surfaces as a function of surface charge and is observed to accumulate at the cell wall of a fungal culture. Taken together, results indicate that nano-scale, fullerene aggregates must be considered appropriately, as they deviate from predictions based on bulk and molecular property estimates.