Our article is a short review of the 9th brochure published by the Bureau International des Poids et Mesures, the BIPM – addressed mainly for physics teachers, pupils and students. This 9th edition of the SI brochure has been prepared following the adoption by the 26th meeting of the CGPM of a set of far-reaching changes. The meeting introduced a new approach to articulating the definitions of the units in general, and of the seven base units in particular, by fixing the numerical values of seven “defining” constants. International System of Units — the way in which the world measures everything from coffee to the cosmos — changed in a way that is more profound than anything since its establishment following the French Revolution.