Descartes’ rule of signs for univariate real polynomials is commonly considered as a fundamental result in real algebraic geometry. It was proposed by René Descartes in 1637 in "La Géométrie", an appendix to his "Discours de la méthode". This rule bounds the number of positive roots of a real univariate polynomial by the signvariation of its coefficients. Only recently generalizations to the multivariate case have been obtained. I will present a new optimal Descartes rule for polynomial systems supported on circuits, obtained in collaboration with Alicia Dickenstein and Jens Forsgård.