In honor of that century of progress, physicists are celebrating 2025 as the International Year of Quantum Science and Technology, as designated by the United Nations. The festivities kick off February 4 with an opening ceremony in Paris, and continue throughout the year with scientific conferences, public lectures and more, including QuantumFest, an event in March at the American Physical Society Global Physics Summit in Anaheim, Calif., featuring hands on activities and demonstrations.

In 1927, a historic gathering took place in Brussels. The Fifth Solvay Conference, attended by some of the most brilliant scientific minds of the 20th century, became a defining moment in the struggle between classical physics and the emerging quantum theory.

Among the 29 attendees, 17 would go on to win Nobel Prizes, including legendary figures such as Albert Einstein, Niels Bohr, and Marie Curie.

This iconic photograph of the event has often been dubbed “the most intelligent photo ever taken,” and for good reason.