Admittedly, the article cited is a bit for scientifically technical for my tastes, but the authors do a brilliant job of explaining when the army was created (210 BC), how they were formed (too technical of a description to be summarized accurately in this small pace) and how the tens of thousands of perfectly formed soldiers, more importantly, kept their precise forms in such unbelievably great shape over the millennia (Polychrome layers applied to these sculpted imperial guards were composed of natural inorganic pigments and binding media. These pigments have been identified as including cinnabar [HgS], apatite [Ca5(PO4)3OH], azurite [Cu3(CO3)2(OH)2] and malachite [Cu2CO3(OH)2], etc., but the precise composition of binding media used in the painting process had long eluded scientists until China scientists discovered a proteinaceous binding media which had been successfully made and applied for the polychrome Terracotta Army.)