  Recent observations have revealed that early-type galaxies (ETG) in clusters
comprise an old galaxy population that is evolving passively. We review some
recent observations from the ground and from HST that show that ETG have
undergone a significant amount of luminosity evolution. This evolution is
traced by two projections of the fundamental plane (FP): the size-magnitude
relation (SMR) and the color-magnitude relation (CMR). We will briefly discuss
the relevance of all these results in the context of the universality of the
IMF.
