Nanomaterials are materials that have at least one external dimension measuring between 1 and 100 nanometers. They can be engineered from minerals and nearly any chemical substance, and they can differ with respect to composition, primary particle size, shape, surface coatings, and strength of particle bonds. Nanomaterials can be classified into organic (carbon-based), inorganic (non-carbon-based), and hybrid (which combine the two) materials. They can occur naturally, be created as the by-products of combustion reactions, or be produced purposefully through engineering to perform a specialized function.

Nanomaterials research takes a materials science-based approach to nanotechnology, leveraging advances in materials metrology and synthesis which have been developed in support of microfabrication research. Materials with structure at the nanoscale often have unique optical, electronic, thermo-physical, or mechanical properties. Due to the ability to generate the materials in a particular way to play a specific role, the use of nanomaterials spans across various industries, from healthcare and cosmetics to environmental preservation and air purification. Nanomaterials have attracted significant research interest because of the unique properties that emerge at the nanometer scale, such as high surface area for chemical reactions, unique surface structures, and different ways of interacting with light.

Currently, very little is known about nanoscale materials and how they affect human health and the environment. NIEHS is committed to supporting the development of nanotechnologies that can be used to improve products and solve global problems in areas such as energy, water, medicine, and environmental remediation, while also investigating the potential risks these materials pose to human health and the environment. Nanotoxicology is the study of the toxicity of nanomaterials.