Holographic principle initially motivated from the black hole physics tries to relate the information in the bulk spacetime to that on the boundary. The applications of the holographic principle to understand cosmology have been started recently.

In my talk, I will give three examples showing that holographic principle is a useful tool to constrain the dark energy model, explain the small l CMB spectrum suppression and we can also devise a holographic dark energy model to expalin the dark energy transition from w > –1 to w < –1.