Two-dimensional histogram of the ratio between the stellar mass surface density derived from full spectral fitting from MUSE (Sect. 5.2.4) and archival stellar mass maps from S⁴G, based on Spitzer IRAC maps (Querejeta et al. 2015), as a function of the light-weighted age of the underlying stellar population in each pixel, derived from the full spectral fitting. We show three galaxies in our sample, spanning the stellar mass range of the PHANGS-MUSE sample (in ascending order from left to right). The figure shows good agreement between the MUSE and the S⁴G mass maps in pixels dominated by stellar populations older than ∼4 Gyr. However, in regions hosting younger populations, the masses derived from the near-IR data are systematically larger, possibly due to the contribution of AGB stars to the near-IR flux. The contours mark the iso-probability curves where the probability density drops below 40% and 10% of the maximum. The dashed red line shows the median mass ratio at a given luminosity-weighted age.