The National Institute of Environment Health Sciences (NIEHS) funds grants to the extramural community with the goal of improving the understanding of how chemical and physical agents cause pathological changes in molecules, cells, tissues, and organs, and how, in response, these changes lead to disease and dysfunction. NIEHS also supports studies of the mechanisms of toxicity of such ubiquitous agents as metals, natural and synthetic chemicals, pesticides, and materials such as asbestos and silica. Specific attention is paid to the effects of these agents on various human organ systems, metabolism, the endocrine and immune systems, and other biological functions.