  The Time Inference with MUSE in Extragalactic Rings (TIMER) project is a
survey with the VLT-MUSE integral-field spectrograph of 24 nearby barred
galaxies with prominent central structures (e.g., nuclear rings or inner
discs). The main goals of the project are: (i) estimating the cosmic epoch when
discs of galaxies settle, leading to the formation of bars; (ii) testing the
hypothesis whereby discs in more massive galaxies are assembled first; and
(iii) characterising the history of external gas accretion in disc galaxies. We
present details on the sample selection, observations, data reduction, and
derivation of high-level data products, including stellar kinematics, ages and
metallicities. We also derive star formation histories and physical properties
and kinematics of ionised gas. We illustrate how this dataset can be used for a
plethora of scientific applications, e.g., stellar feedback, outflows, nuclear
and primary bars, stellar migration and chemical enrichment, and the gaseous
and stellar dynamics of nuclear spiral arms, barlenses, box/peanuts and bulges.
Amongst our first results - based on a few selected galaxies -, we show that
the dynamics of nuclear rings and inner discs is consistent with the picture in
which they are formed by bars, that the central few hundred parsecs in massive
disc galaxies tend to show a pronounced peak in stellar metallicity, and that
nuclear rings can efficiently prevent star formation in this region. Finally,
we present evidence that star-bursting nuclear rings can be fed with
low-metallicity gas from low-mass companions.
