  Differential cross section measurements of the associated production of top
quark and b quark pairs, $\text{t}\bar{\text{t}}\text{b}\bar{\text{b}}$, are
presented. The results are based on data from proton-proton collisions
collected by the CMS detector at the LHC at a centre-of-mass energy of
$\sqrt{s} = 13\text{ TeV}$, corresponding to an integrated luminosity of $138
\text{ fb}^{-1}$. Four fiducial phase space regions are defined targeting
distinct aspects of the $\text{t}\bar{\text{t}}\text{b}\bar{\text{b}}$ process.
Kinematic variables are defined at the stable particle level and distributions
are unfolded to the particle level through maximum likelihood fits. The cross
sections are measured in the lepton+jets decay channel of the top quark pair,
using events with exactly one isolated electron or muon and at least five jets.
The results are compared with predictions from several event generators. The
differential measurements have relative uncertainties in the range of
$2\!-\!50\%$, depending on the phase space and the observable.
