One of the best pairs to study theta correspondence is for (Mp(2n), SO(2n+1)), whose study was pioneered by Waldspurger for n =1, and then carried out by Adams-Barbasch for Archimedean fields, and Gan-Savin for p-adics. In this lecture we attempt theta correspondence not between irreducible representations, but in a more categorical sense, hoping for an equivalence of categories --- though it is not!, bringing one to a question studied in algebraic geometry, ``derived equivalence" of algebraic varieties.