The behaviour of electrons and holes in a crystal lattice is a fundamental quantum phe-nomenon,accounting for a rich variety of material properties.Boosted by the remarkable electronic and physical properties of two-dimensional materials such as graphene and topological insulators,transition metal dichalcogenides(TMDs) have recently received renewed attention.In this context,the anomalous bulk properties of semimetallic WTe2 have attracted considerable interest.Recently it was found that WTe2 exhibits extremely large uniaxial magnetoresistance along the crystallographic c-axis [1],attributed to a balanced electron-hole resonance,and it was further predicted to realize the first Weyl-II type quantum phase [2].In this talk we report first-principles calculations and angle-and spin-resolved photoemis-sion spectroscopy measurements on WTe2 [3],through which we provide clear evidence that the electronic properties of WTe2 display a layer-dependent evolution from surface to bulk,that is,it cannot be considered a priori as a non-interacting 2D-layered system.The balance between the hole and electron states,representing one of the crucial conditions for the nonsaturating magnetoresistance in this system,is established only beyond finite number of layers(three)and maintained in the bulk.This consideration provides a fundamental input for future exploitation of TMDs in general,and WTe2 in particular,in devices and heterogeneous interfaces.Moreover,the Weyl properties of WTe2 are presented,and compared with the one of strained HgTe,the most famous topological insulator.In fact,recently HgTe has been theoretically predicted to be an ideal Weyl semimetal under compressive strain,and in this talk we will show new results that shed more light on the interplay between topological properties and Weyl states [4].