2019 is a very special year in chemistry. 2019 marks two major anniversaries: the 100th anniversary of the founding of the International Union of Pure and Applied Chemistry (IUPAC), and the 150th anniversary of Dimitri Mendeleev’s first publication on the Periodic Table of Elements . IUPAC is the global organization that, among many other things, established a common language for chemistry—enabling scientific research, education, and trade. In a similar manner, Mendeleev’s system classified all the elements that were known at the time, and even predicted the existence of elements that would only come to be discovered years later. These two anniversaries are closely entwined, as IUPAC has played a major role developing of the modern Periodic Table by ensuring that the most authoritative version of the table is accessible to everyone , establishing names and symbols for the newly discovered elements, and also constantly reviewing its accuracy through the IUPAC Commission on Isotopic Abundances and Atomic Weights.