The Metric System, now known as the International System of Units (SI), was adopted by the National assembly in France on 10 December 1799. The basic principles were decimalization, open access, and measurement units based on nature. The Treaty of the Metre that formally established the Metric System was signed on 20 May 1875 and ratified by United States in 1878. On 20 May 2019, the 144th anniversary of the signing of the 1875 Metre Convention, the world celebrated the biggest revolution in measurement units since the French Revolution. On that day, all of the base units of the SI became defined by fixed values of the fundamental constants or properties of nature. The redefinition effectively realized the original goals of the founders of the Treaty of the Metre. The following provides a brief history of human measurement systems from the ancient Egyptians to the development of the SI and on to the science and technology that gave birth to historical redefinition.