And what do the subspheres contain? A mixture similar to the liquid that surrounds them in the spheres. First, water. Dissolved in the water, proteins: hen blood proteins outside the subspheres; inside, phospho-rus-rich proteins that bind up most of the egg’s iron supply. And suspended in the water, subsubspheres about 40 times smaller than the subspheres, some of which turn out to be familiar from the human body. The subsubspheres are aggregates of four different kinds of molecules: a core of fat surrounded by a protective shell of protein, cholesterol, and phospholipid, a hybrid fat-water mediator which in the egg is mainly lecithin. Most of these subsubspheres are “low-density lipoproteins,” or LDLs—essentially the same particles that we keep track of in our own blood to monitor our cholesterol levels