On 16 November 2018, the member states of the Metre Convention, at the 26th General Conference on Weights and Measures (CGPM) in Versailles, France voted to revise the International System of units (SI) and thus change the definition of the kilogram, the ampere, the kelvin and the mole [1]. All SI units are now defined in terms of fundamental constants: specific physical quantities that we believe to be perfectly stable in time and across the universe.