Inorganic chemists study reactions of metals and main group elements. Their research involves synthesis of new compounds and materials. After characterizing the compounds, they apply them to problems such as human illness, pollution, catalysis, and new electronic and structural materials. Inorganic chemists often bond organic molecules to metals, use physical chemistry to characterize their compounds, analyze other compounds with what they have synthesized, or study the role of metals in biological systems. As they do research, they make discoveries in bioinorganic, organometallic, materials, and coordination chemistry.