While there’s not a clear, punctuating distinction between ancient and modern chemistry, there are a few major differences that separate the two. Modern chemists describe the world in terms of atoms, molecules, and electrons and have a relatively complete understanding of the basic particles that make up matter—at least insofar as is necessary to describe chemical transformations. Ancient chemists didn’t have this information and relied less on experimental evidence and more on theory and mythology. For example, ancient chemists sought the Philosopher’s Stone (see below), for which there was no verifiable evidence, but they were attracted to it for its mythological power to preserve youth.