Special instances of Shimura varieties were originally introduced by Goro Shimura in the course of his generalization of the complex multiplication theory. Shimura showed that while initially defined analytically, they are arithmetic objects, in the sense that they admit models defined over a number field, the reflex field of the Shimura variety.
Goro Shimura introduced special cases of Shimura varieties in his development of complex multiplication theory. He demonstrated that these initially analytical entities transform into arithmetic objects by admitting models defined over a number field—their reflex field—thus enriching their mathematical significance beyond mere analysis.