Electron valleys are extrema in the band structure of solids like semiconductors. Traditional semiconductor electronics works on the control of electron flow in semiconductors. But transition metal dichalcogenides (TMDCs) are a new class of two-dimensional-semiconductors in which we can also control the electron valley. The valley degree of freedom here is coupled with spin and paves way for a whole new generation of quantum switching devices. In this presentation, I will report our spectroscopy studies on modification of excitons and phonons under strain in TMDCs.