Formalin is a solution of formaldehyde gas in water, typically containing about 37% formaldehyde by weight. It is commonly used as a disinfectant and preservative in laboratories and medical settings. Due to its ability to kill bacteria and preserve biological specimens, formalin is essential in histology and pathology. In addition to its use in scientific applications, formalin is also found in some household products, such as disinfectants and preservatives in cosmetics. However, exposure to formaldehyde can pose health risks, including irritation of the eyes, skin, and respiratory system, making proper handling and ventilation important.