  We analyze the spatially resolved star formation history of 300 nearby
galaxies from the CALIFA integral field spectroscopic survey to investigate the
radial structure and gradients of the present day stellar populations
properties as a function of Hubble type and galaxy stellar mass. A fossil
record method based on spectral synthesis techniques is used to recover
spatially and temporally resolved maps of stellar population properties of
spheroidal and spiral galaxies with masses $10^9$ to $7 \times 10^{11}$
M$_\odot$. The results show that galaxy-wide spatially averaged stellar
population properties (stellar mass, mass surface density, age, metallicity,
and extinction) match those obtained from the integrated spectrum, and that
these spatially averaged properties match those at $R = 1$ HLR (half light
radius), proving that the effective radii are really effective.
  Further, the individual radial profiles of the stellar mass surface density
($\mu_\star$), luminosity weighted ages ($< {\rm log}\,age>_L$), and mass
weighted metallicity ($< \log Z_\star >_M$) are stacked in bins of galaxy
morphology (E, S0, Sa, Sb, Sbc, Sc and Sd). All these properties show negative
gradients as a sign of the inside-out growth of massive galaxies. However, the
gradients depend on the Hubble type in different ways. For the same galaxy
mass, E and S0 galaxies show the largest inner gradients in $\mu_\star$; while
MW-like galaxies (Sb with $M_\star \sim 10^{11} M_\odot$) show the largest
inner age and metallicity gradients. The age and metallicity gradients suggest
that major mergers have a relevant role in growing the center (within 3 HLR) of
massive early type galaxies; and radial mixing may play a role flattening the
radial metallicity gradient in MW-like disks.
