The inner cells are alive, at least until the onion (a root) is harvested. The outer layers, like our outer skin, are dead material. Fresh onions, like flower bulbs, have the potential to grow into a new plant. --------------------------------------------- Initially an onion cell is alive, but later it is dead. For example when the farmer first digs up his onion crop all the onion cells in the onions are usually alive, but as the onions are left out to dry the onion cells on the outside become dehydrated and die forming an outer "onion skin" of onion cells that are dead that protects the onion flesh inside composed of onion cells that are alive. When we cook onions the onion cells die. When we eat uncooked fresh onions the stomach acid and other digestive juices kill the onion cells.