Today, May 20, marks the International Day of Metrology, in commemoration of the signature in Paris of the Metro Treaty, in 1875, which established a common system of unit measurement known as the International System of Units (SI). The theme of World Metrology Day 2019 is “The International System of Units – Fundamentally better”. This theme was chosen because, on November 16, 2018, the General Conference on Weights and Measures agreed perhaps one of the most important revisions of the International System of Units (SI) since its inception. In fact, metrology, the science of measurement, plays a central role in scientific discovery and innovation, industrial manufacturing and international trade, in the improvement of the quality of life and in the protection of the global environment. The World Metrology Day project is carried out jointly by the BIPM and the OIML. We hope you enjoy events and activities held in your countries. Happy Metrology Day!