AbstractThe photometric and RV techniques, although extremely efficient to detect and characterize planets, are, however, indirect techniques (as well as astrometry). Phenomena such as stellar pulsation, inhomogeneous convection, spots or magnetic cycles can prevent us from finding planets or they might degrade the parameters estimation. We will consider the challenges related to the knowledge of stellar activity for the next decade: detect telluric planets in the habitable zone of their stars (from G to M dwarfs), understand the activity in the low-mass end of M dwarf (on which will focus future near-infrared high-resolution spectrograph like SPIRou or CARMENES), limitation to the process of summing several transit observations (in order to characterize the atmospheric components) due to the variability of stellar activity (from the ground or with Spitzer or JWST), as well as the methods proposed and used to overcome this issue.