While most of the planets discovered so far have been found orbiting around solar-type stars, low-mass stars have been recognised as a "shortcut" to glance into an exo-life laboratory. Currently, stellar activity is one of the most limiting factors for achieving the precision required to detect Earth-twins via the radial velocity method. Understanding the chromospheres of M dwarfs is crucial to solve this problem. In this contribution we present a study of the activity-rotation-stellar parameters and flux-flux relationships among a large sample of early-M dwarfs which are currently being monitored in the framework of the HADES (HArps-n red Dwarf Exoplanet Survey) radial velocity survey (see also the posters by Affer et al., and Scandariato et al.).