Observation of Higgs boson production in association with a top quark pair: A probe of fundamental interest to further explore the nature of the Higgs boson is to measure its interaction with the top-quark, the most massive particle in the Standard Model. Indirect measurements of this interaction were previously made assuming no contribution from unknown particles. A more direct test of this coupling can be performed through the direct production of the Higgs boson in association with a top-quark pair, ttH. Measuring this process is challenging, because it is extremely rare: only one percent of Higgs bosons are expected to be produced this way. As submit to Physics Letters B (2018), using advanced analysis techniques, several independent searches for ttH production have been performed and combined, yielding the first observation of ttH production with a significance of 6.3 standard deviations relative to the background-only hypothesis.