If you have to ask, chances are you are not celebrating Mole Day, an unofficial holiday for chemists, on October 23, between 6:02 AM and 6:02 PM. The time and date are based on Avogadro's number, which defines the number of particles in one mole of substance. Emory chemists celebrate in a big way. Their tradition involves a pinata, this year hand-crafted into an actual garden-variety mole by Charlene Chan and Yoshie Narui, and some initiation rites for new faculty members (see Chris Scarborough in action in the video below). Cheers to Avogadro, and to scientists everywhere today.