The redshifted 21-cm background is expected to be a powerful probe of the early Universe bearing both cosmological and astrophysical information from a wide range of redshifts.

We use semi-numerical computational methods to generate histories of the 21-cm signal, accounting for the inhomogeneous backgrounds of Lyman-alpha, X-ray, Lyman-Werner and ionizing radiation. 

In particular, the power spectrum of fluctuations in the 21-cm brightness temperature is anisotropic due to the line-of-sight velocity gradient produced by the density fluctuations, and in this talk I will show how we can extract from it information about the earliest heating sources.