National Periodic Table Day is observed in the USA every February 7 to celebrate the significance of the periodic table of elements and honor the scientists who contributed to its development. The holiday was founded by David T. Steineker, a public school chemistry teacher, to recognize John Newlands, who published an early version of the periodic table in 1863. The periodic table itself, which organizes chemical elements based on their atomic numbers and properties, was significantly advanced by Dmitri Mendeleev, who published his version in 1869. Celebrations often include sharing interesting facts about the periodic table, engaging in chemistry trivia challenges, enrolling in online chemistry courses, and supporting local STEM programs for underprivileged children. Participants are encouraged to use social media to promote the holiday with hashtags like #NationalPeriodicTableDay.