  With detections of quasars powered by increasingly massive black holes (BHs)
at increasingly early times in cosmic history over the past decade, there has
been correspondingly rapid progress made on the theory of early BH formation
and growth. Here we review the emerging picture of how the first massive BHs
formed from the primordial gas and then grew to supermassive scales. We discuss
the initial conditions for the formation of the progenitors of these seed BHs,
the factors dictating the initial masses with which they form, and their
initial stages of growth via accretion, which may occur at super-Eddington
rates. Finally, we briefly discuss how these results connect to large-scale
simulations of the growth of supermassive BHs over the course of the first
billion years following the Big Bang.
