Dinitrogen tetroxide, with the chemical formula N2O4, is a colorless gas that can also exist as a pale yellow liquid. It is composed of two nitrogen atoms and four oxygen atoms. This compound is known for its role as an oxidizer in rocket propellants and is often used in the aerospace industry. At room temperature, dinitrogen tetroxide can easily convert to its dimer, N2O4, which is in equilibrium with its monomer, NO2. It has a sweet, acrid smell and is highly toxic, requiring careful handling. Its properties make it useful in various chemical reactions and industrial applications.