  Recent integral-field spectroscopy observations have revealed that thick- and
thin-disk star-formation histories are regulated by the interplay of internal
and external processes. We analyze stellar-population properties of 24 spiral
galaxies from the AURIGA zoom-in cosmological simulations, to offer a more
in-depth interpretation of observable properties. We present edge-on maps of
stellar age, metallicity and [Mg/Fe] abundance, and we extract the
star-formation and chemical-evolution histories of thin and thick disks. Both
show signs of the interplay between internal chemical enrichment and gas and
star accretion. Thick disks show particularly complex stellar populations,
including an in-situ component, formed from both slowly enriched and accreted
more pristine gas, and an additional significant fraction of ex-situ stars.
