Princeton researchers performed quantum transport studies of the insulator bulk of monolayer WTe2, a large gap 2D topological insulator. Surprisingly, the phenomenon of Landau quantization strikingly develops in the insulator state. This is highly unexpected as in established quantum theory of materials, Landau quantization are the quantum characteristics of metals, not insulators. This discovery calls for the understanding of a class of novel correlated insulators that may host hidden quantum excitations.