Formaldehyde is an aldehyde, a simple organic compound with the chemical formula $\text{CH}_2\text{O}$. At standard temperature and pressure, it exists as a colorless gas, and its aqueous solution, formalin, is a widely used reagent. Chemically, it is characterized by the presence of an aldehyde functional group, making it highly reactive. Due to its cross-linking properties, formaldehyde is utilized in various industrial applications, including the manufacture of resins, particularly those used in adhesives for plywood and particleboard. In biological and material science contexts, it functions as a fixative, preserving biological materials by reacting with amino groups in proteins, which stabilizes the tissue structure for subsequent analysis.