Kepler’s contributions reached far beyond the realm of astronomy, to meteorology, mathematics, geology, mineralogy and crystallography. Kepler published this 24-page pamphlet, a study of the snowflake, as a New Year’s greeting for a friend. Kepler distinguished the way organisms grow, by differentiation, from the growth of crystals like the snowflake by accretion. The work stimulated inquiry in mineralogy for the next century. As recently as 1998, Thomas Hales provided a mathematical proof of what became known as “Kepler’s conjecture” from this book about crystal packing.