Recent searches for the production of a Higgs boson (H) in association with a top quark pair (${\rm t\bar{t}H}$) by the CMS Collaboration are presented. They are performed using 36 fb$^{-1}$ of LHC pp collision data at $\sqrt{s}$=13 TeV collected in 2016. The analyses exploit several Higgs boson decay channels, together with different top quark decay modes. The results combined with previous searches yield the first observation of the ${\rm t\bar{t}H}$ production process. An excess of events is observed with a significance of 5.2 standard deviations over the expectation from the background-only hypothesis. The combined best fit signal strength normalized to the standard model prediction is 1.26$^{+0.31}_{-0.26}$.