The landmark change to the official definition of a kilogram, the internationally accepted basic unit of mass, came into effect Monday.

No longer based off of the manmade platinum-iridium alloy cylinder tucked away in a high security vault in Paris, France, a kilogram will now officially be measured using atomic properties and physics constants.

Scientists and researchers had been battling it out for years on how to best update the basic unit of measurement, citing concerns that every time the standard kilo was handled, it would shed atoms and cause its mass to be slightly changed.

Wolfgang Ketterle, a professor of physics at MIT and Nobel Prize winner, explained the new definition of the kilo as the “equivalent to the mass of a specified number of photons (particles of light) which would be trapped in a cavity between mirrors… so that they could be weighed on a standard scale” in the MIT newsletter.

The new definition is expected to be more accurate when measuring very small or very large masses and alleviates scientists relying on a physical object to base their calculations on.