A natural toxin is a poisonous chemical produced by a living organism without human intervention, found across plants, fungi, algae, and animals. Well-known food examples include solanine and chaconine in green potatoes, cyanogenic glycosides in bitter almonds and cassava, lectins in undercooked kidney beans, aflatoxins from Aspergillus moulds on peanuts and cereals, marine biotoxins in shellfish such as saxitoxin, and histamine from poorly chilled fish. Plants evolved these compounds as defences against pests and predators, and concentrations rise with stress, damage, or improper storage. Food safety regulation manages them through maximum limits, harvest controls, and processing advice such as peeling potatoes or soaking and boiling beans. Unlike pesticide residues, they are inherent to the food itself.