2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/52740We sketch the construction of a gauge invariant Exact Renormalization Group (ERG). Starting from Polchinski's equation, the emphasis is on how a series of ideas have combined to yield the gauge invariant formalism. A novel symmetry of the ERG allows the flow equation to be modified, in such a way that it is suitable for the computation of the (universal) two-loop beta-function. This computation has now been performed, within the framework of the ERG and, as such, in a manifestly gauge invariant way for the very first time.10 pages, 1 figure. Proceeding of Quarks-2004, Pushkinskie Gory, Russia, May 24-30. v2: minor corrections compared to published versionHigh Energy Physics - Theorytext