Almonds are the world’s largest tree-nut crop. They’re the seed of a plum-like stone fruit, or drupe; the tree is a very close relative of the plum and peach. There are several dozen wild or minor species, but the cultivated almond, Prunus amygdalus, came from western Asia and had been domesticated by the Bronze Age. California is now the largest producer. Thanks to their high content of antioxidant vitamin E and low levels of polyunsaturated fats, almonds have a relatively long shelf life.