  Recent measurements dedicated to improving the understanding of modelling top
quark pair (${\text{t}\overline{\text{t}}}$) production at the LHC are
summarised. These measurements, performed with proton-proton collision data
collected by the CMS detector at $\sqrt{s}=$ 13 TeV, probe the underlying event
in ${\text{t}\overline{\text{t}}}$ events, and use the abundance of jets in
${\text{t}\overline{\text{t}}}$ events to study the substructure of jets. A new
set of tunes for PYTHIA 8, and their performance with
${\text{t}\overline{\text{t}}}$ data, are also discussed.
