Chemistry, in one form or another, has been practiced for thousands of years—but for most of that time, it was more akin to wizardry than the hard science we know today. The alchemists of old wielded a strange and marvelous power, to mix two substances and create something entirely new, something that couldn't be separated back into its original parts...except by more alchemy. Through trial and error, mixing up ingredients that seemed like they might be powerful—smelly sulfur, or metals like mercury—we slowly gathered enough pieces of the puzzle that clever people began to see the outlines of the whole shape: the Periodic Table.