Stellar mass surface density − age relationship for all of the 98 291 individual zones in the 107 galaxies. Small points are color coded by the stellar mass of the galaxy to which they belong (upper panel) and by the distance of each zone to the nucleus of the galaxy in units of HLR (bottom panel). The circles are color coded by galaxy mass and represent the global and ⟨log  age relation. The line in the bottom panel shows the result of a second-order polynomial fit.