2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/100184Lie algebroids can not always be integrated into Lie groupoids. We introduce a new object--``Weinstein groupoid'', which is a differentiable stack with groupoid-like axioms. With it, we have solved the integration problem of Lie algebroids. It turns out that every Weinstein groupoid has a Lie algebroid and every Lie algebroid can be integrated into a Weinstein groupoid.a proof improvedDifferential GeometryAlgebraic Geometrytext