In this talk I will present results from studies on the cosmology in the presence of new degrees of freedom in the gravitational sector. The new degrees of freedom can be classified according to their spins, and this talk will be focused mainly on spin-0 and spin-2 cases. In particular, I will talk about the screened modified gravity theories, including f(R) gravity, chameleon theory, DGP model and Galileon gravity. In such theories, the new degrees of freedom are hidden locally but can have detectable imprints on cosmological observables. I will show how these degrees behave in cosmology, and explain how to best constraint them.