I will review the classification of 6D superconformal field theories from string
theory and Calabi--Yau geometry, and highlight how this can reveal a wealth of
information about lower dimensional superconformal field theories via
compactification. I will show that each 4D N=2 Class S theory, consisting of the
6D N=(2,0) theory compactificed on a three-punctured sphere, where one of the
punctures is a simple puncture, has a realisation as a compactification on a
torus of a 6D N=(1,0) SCFT. Further, the Higgs branch RG flows/complex structure
deformations on the N=(1,0) side are related to the Coulomb branch deformations
between the Class S theories.