  3C84 (NGC1275) is one of the brightest radio sources in the mm radio-bands,
which led to a plethora of VLBI observations at numerous frequencies over the
years. They reveal a two-sided jet structure, with an expanding but not
well-collimated parsec-scale jet, pointing southward. High resolution mm-VLBI
observations allow the study and imaging of the jet base on the sub-parsec
scale. This could facilitate the investigation of the nature of the jet origin,
also in view of the previously detected two-railed jet structure and east-west
oriented core region seen with RadioAstron at 22 GHz. We produce VLBI images of
this core and inner jet region, observed during the past twenty years at 15,
43, and 86 GHz. We determine the kinematics of the inner jet and ejected
features at 43 and 86 GHz and compare their ejection times with radio and
$\gamma$-ray variability. For the moving jet features, we find an average
velocity of $\beta^\textrm{avg}_\textrm{app} = 0.055-0.22$c ($\mu^\textrm{avg}
= 0.04-0.18\,$mas/yr). From the time-averaged VLBI images at the three
frequencies, we measure the transverse jet width along the bulk flow. On the
$\leq 1.5$ parsec scale, we find a clear trend of the jet width being frequency
dependent, with the jet being narrower at higher frequencies. This
stratification is discussed in the context of a spine-sheath scenario, and is
compared to other possible interpretations. From quasi-simultaneous
observations at 43 and 86\,GHz we obtain spectral index maps, revealing a
time-variable orientation of the spectral index gradient, due to structural
variability of the inner jet.
