Jets playing hide and seek

I will discuss recent progress that has been made on jet reconstruction techniques. I will concentrate on how one can deal with unwanted soft background contributions to the jet. I will start with the case of the underlying event and discuss the cone algorithm(s). Then I will proceed with the more dramatic cases of pileup in pp collisions and underlying evernts in heavy-ion collisions, for which I will introduce the concept of jet areas and show how to use them to subtract the soft background.