Abstract: With reduced dimensionality, materials always display unique physical properties that differ greatly from their bulk counterparts, at the same time exhibiting novel quantum states. Two-dimensional (2D) Group-VI transition metal dichalcogenides (TMD), a newly emerging class of atomically thin semiconductors, have sizeable direct band gaps. Additionally, in the first Brillouin zone, there are degenerate but nonequivalent valleys which are well separated in momentum space. Due to the inversion symmetry breaking in their monolayer form, at different valleys in the Brillouin zone the electrons or holes carry non-zero but contrasting orbital magnetic moments and Berry curvatures, which provide the prerequisites of quantum manipulation of the valley degree of freedom with an external stimulus. We present here a brief overview of the valleytronics of 2D TMDs, followed by some perspectives on potential developments.