  We present a multi-component structural analysis of the internal structure of
$1074$ high redshift massive galaxies at $1<z<3$ from the CANDELS HST Survey.
In particular we examine galaxies best-fit by two structural components, and
thus likely forming discs and bulges. We examine the stellar mass, star
formation rates, and colours of both the inner `bulge' and outer `disc'
components for these systems using SED information from the resolved ACS+WFC3
HST imaging. We find that the majority of both inner and outer components lie
in the star-forming region of UVJ space ($68$ and $90$ per cent respectively).
However, the inner portions, or the likely forming bulges, are dominated by
dusty star formation. Furthermore, we show that the outer components of these
systems have a higher star formation rate than their inner regions, and the
ratio of star formation rate between `disc' and `bulge' increases at lower
redshifts. Despite the higher star formation rate of the outer component, the
stellar mass ratio of inner to outer component remains constant through this
epoch. This suggests that there is mass transfer from the outer to inner
components for typical two component forming systems, thus building bulges from
disks. Finally, using Chandra data we find that the presence of an AGN is more
common in both $1$-component spheroid-like galaxies and $2$-component systems
($13\pm3$ and $11\pm2$ per cent) than in $1$-component disc-like galaxies
($3\pm1$ per cent), demonstrating that the formation of a central
inner-component likely triggers the formation of central massive black holes in
these galaxies.
