Rodge, for the simplicity of it's ingredients,there's no more complicated food on the planet than bread. To fully explain the effects of each ingredient, you'd need:
Water: a 400 page book
Oil: a 30 page pamphlet
Yeast: a 1600 page book
Salt: a 400 page book
Sugar: a 400 page book
and that's to cover what we know now/current theories. There's still lots that we don't know/understand about bread.