The periodic table of elements is a familiar image for anyone who has spent time in a chemistry classroom, but despite all the information packed into those classic wall posters students today need to understand more than just the elements. This is the inspiration behind Isotopes Matter, a set of interactive educational resources from the International Union of Pure and Applied Chemistry (IUPAC). Visitors to Isotopes Matter will find a colorful interactive periodic table where clicking on each element brings up information on its isotopes, highlights a current use of that element, and links to a PDF with further isotopic information. In addition to this, Isotopes Matter also provides a set of peer-reviewed educational resources about isotopes and their atomic weights, which may be helpful for chemistry learners and teachers alike. Launched in 2016, these resources were created to accompany the IUPAC Isotopic Periodic Table and "designed to communicate the importance of isotopes and their diverse applications, while helping students and educators understand why atomic weight intervals have been introduced for some elements and how they should be used."