  From an observational standpoint, stellar activity poses a critical challenge
to exoplanet science, as it inhibits the detection of planets and the precise
measurement of their parameters. Radial velocity and transit searches revealed
a significant fraction of exoplanet hosts is active, and showed the need to
fully understand the different facets of stellar activity and its impact on
observables. Moreover, the activity correction is of prime importance for the
detection and characterisation of Earth analogues. We present a review of the
effects that stellar activity features such as starspots, faculae, and stellar
granulation have on photometric and low-resolution spectroscopic observations
of exoplanets, and discuss the main aspects of the techniques which were
developed to reduce their impact.
