Measurements of ${\rm t\bar t+jets}$, ${\rm t\bar t+b\bar b}$ production, and ${\rm t\bar tt\bar t}$ production at CMS

The most recent CMS measurements of the production of ${\rm t\bar t}$ pairs with two additional jets, or two additional b quarks, are presented. These two processes are important for several reasons: they can allow a better modeling of Monte Carlo simulations, because of the different energy scale associated to b-jets and generic jets; they are important backgrounds to other standard model processes; and they might be related to new physics. In addition, the search for the production of two ${\rm t\bar t}$ pairs is discussed, along with its connection to the Yukawa coupling of top quarks to the Higgs boson.