Title:Emphasizing the possible lineage between Ellipticals and Lenticulars galaxies in the infrared Abstract: Early-type galaxies (ETGs), including Ellipticals (E) and Lenticulars (S0) are among the most massive galaxies today. Their poorly known formation is still subject to much debate. First believed to have simple, static and old stellar populations, they actually present a complex star formation history. It has already been shown that Lenticulars can be significantly more luminous than Ellipticals. In this talk, I will discuss more the differences between E and S0 mainly though a study of a sample of 24 um selected ETGs in the local Universe. And I will also present a study of the E and S0 in rich environments, comparing these populations in two clusters at different stages in their evolution, Virgo and Coma.