SED fitting is a very versatile tool. From a rough estimation of the stellar masses of distant galaxies to the search for small subpopulations of stars in high S/N spectra, it can be applied to a large part of the problems in galaxy evolution. This is the strength and the weakness of the SED fitting technique: it does it all at once.
We highlight here a few significant results. The intention is not to be complete or to mention the work that has been most in view, but rather to highlight the diversity of questions that can be adressed from fitting the integrated SEDs of stellar populations. Particular importance has been given to supply cautionary remarks, as it is easy to overinterpret the significance of the derived properties, in view of the complexity of the physical mechanisms and our frequent lack of detailed understanding.