Original kilogram replaced — new International System of Units (SI) entered into force

In addition to Ampere, Kelvin, Mol and Co., the kilogram also is now defined by a natural constant. In concrete terms, this means that the original kilogram, which has been the measure of all things for 130 years, has now served its purpose in Paris. This is made possible by the single crystals grown from the highly enriched isotopic silicon-28 at the Leibniz-Institut für Kristallzüchtung (IKZ).
Source: EurekaAlert, https://www.eurekalert.org