  We review the current status of knowledge concerning the early phases of star
formation during cosmic dawn. This includes the first generations of stars
forming in the lowest mass dark matter halos in which cooling and condensation
of gas with primordial composition is possible at very high redshift ($z >
20$), namely metal-free Population III stars, and the first generation of
massive black holes forming at such early epochs, the so-called black hole
seeds. The formation of black hole seeds as end states of the collapse of
Population III stars, or via direct collapse scenarios, is discussed. In
particular, special emphasis is given to the physics of supermassive stars as
potential precursors of direct collapse black holes, in light of recent results
of stellar evolution models, and of numerical simulations of the early stages
of galaxy formation. Furthermore, we discuss the role of the cosmic radiation
produced by the early generation of stars and black holes at high redshift in
the process of reionization.
