We show how the investigation of the redshifted 21-cm radiation can give insight into the development of structures in the early universe (at redshifts z>5). In particular we investigate: the epoch of the first light; the fluctuations in the redshifted 21-cm emission induced by the density inhomogeneities in CDM dominated universes; the emission and absorption shells that are generated around the first bright quasars. Such features can be observed with the next generation radio facilities.