May 20 marks the anniversary of the signing of the Metre Convention in Paris in 1875 by representatives of seventeen nations, an agreement that laid the foundation for international cooperation in metrology — the science of measurement — and its industrial, commercial, and societal applications. The International Committee for Weights and Measures formally established World Metrology Day in 1999 to mark this anniversary. The Convention's original aim of achieving worldwide uniformity in measurement remains as vital today as it was 150 years ago, underpinning nearly everything from international trade and industry to healthcare, scientific research, and modern technologies such as artificial intelligence and space exploration. The day is marked through events organized by national metrology institutes and scientific bodies worldwide, including seminars on advances in measurement science, public exhibitions explaining how base units like the kilogram, metre, and second are defined, and discussions on how precise measurement supports innovation and fair trade between nations.