After they were discovered three decades ago, counter-rotating galaxies still represent a challenging subject for both theorists and observers. Although the broad picture of the formation of counter-rotating galaxies is in place, we still miss many details.
A few issues should be attacked first in the near future to make a step forward in our understanding of counter-rotation in disk galaxies. They include: a deep imaging survey to look for the fingerprints of accretion and merging events in the environment of counter-rotating galaxies at very low levels of surface brightness; the analysis of a complete sample of spiral galaxies to drive unbiased conclusions about the frequency of the different kinds of counter-rotation; the derivation of the stellar LOSVD from high (spectral and spatial) resolution data obtained with wide-field integral-field units to look for yet undetected retrograde stars; and the extensive measurement of the stellar populations of the prograde and retrograde components in counter-rotating galaxies to test the predictions of the different formation scenarios.