Myoglobin is the heme-containing protein in muscle that stores oxygen and delivers it to the working fibres, and together with haemoglobin it determines meat colour. Muscles used for sustained activity carry more of it, which is why chicken leg meat is darker than breast meat and why beef is redder than pork. Its chemistry drives retail display life: oxygenation forms bright-red oxymyoglobin, the bloom consumers expect, while oxidation to brown metmyoglobin signals staleness. Processors manage packaging atmospheres, antioxidants, and lighting to hold the desirable red state, and cured meats fix a pink colour through nitrosylmyoglobin formation.