Status of Intersection Theory and Feynman Integrals

We give a pedagogical review of the recently-introduced notion of a “scalar product” between Feynman integrals and how it helps us understand the analytic structure of the perturbative S-matrix. (This article is a contribution to the proceedings of the workshop “MathemAmplitudes 2019: Intersection Theory and Feynman Integrals” held in Padova, Italy on 18-20 December 2019.)