Example of the evolutionary scheme for interacting and merging galaxies described in Sect. 2.1. Top: SDSS r-band images of galaxies included in the CALIFA survey, from left to right: pre-merger stage, well-defined separation between the galaxies, no evident interaction signatures (IC 0944 and KUG 1349+143); merger stage: two defined nuclei with evident interaction features (NGC 169 and NGC 169A); post-merger stage, single extended nucleus in optical with prominent tidal features (NGC 2623); merger remnant stage, possible tidal debris (NGC 5739). Middle: stellar velocity fields. Bottom: Hα+[NII] velocity field for each galaxy example. Contours represent the continuum obtained from the data cubes. We note that for these objects the velocity field distributions are extracted from a single IFU data cube, except for the pairs of galaxies in the pre-merger stage, where each galaxy has its own IFU data cube. The size of each box is 2 arcmin. Top is north and left is east.