  In this paper, we use stacking analysis to trace the mass-growth, colour
evolution, and structural evolution of present-day massive galaxies
($\log(M_{*}/M_{\odot})=11.5$) out to $z=5$. We utilize the exceptional depth
and area of the latest UltraVISTA data release, combined with the depth and
unparalleled seeing of CANDELS to gather a large, mass-selected sample of
galaxies in the NIR (rest-frame optical to UV). Progenitors of present-day
massive galaxies are identified via an evolving cumulative number density
selection, which accounts for the effects of merging to correct for the
systematic biases introduced using a fixed cumulative number density selection,
and find progenitors grow in stellar mass by $\approx1.5~\mathrm{dex}$ since
$z=5$. Using stacking, we analyze the structural parameters of the progenitors
and find that most of the stellar mass content in the central regions was in
place by $z\sim2$, and while galaxies continue to assemble mass at all radii,
the outskirts experience the largest fractional increase in stellar mass.
However, we find evidence of significant stellar mass build up at
$r<3~\mathrm{kpc}$ beyond $z>4$ probing an era of significant mass assembly in
the interiors of present day massive galaxies. We also compare mass assembly
from progenitors in this study to the EAGLE simulation and find qualitatively
similar assembly with $z$ at $r<3~\mathrm{kpc}$. We identify $z\sim1.5$ as a
distinct epoch in the evolution of massive galaxies where progenitors
transitioned from growing in mass and size primarily through in-situ star
formation in disks to a period of efficient growth in $r_{e}$ consistent with
the minor merger scenario.
