Metallothionein is a small, cysteine-rich protein found in many organisms, including humans. It plays a crucial role in binding and regulating essential metals like zinc and copper, as well as detoxifying harmful heavy metals such as cadmium and mercury. This protein helps maintain metal homeostasis and protects cells from oxidative stress. Additionally, metallothionein is involved in various biological processes, including cell growth, immune response, and apoptosis (programmed cell death). Its expression can be influenced by factors such as diet, environmental toxins, and hormones, making it an important focus in studies related to toxicology and nutrition.