In this talk, we will show, how the viable f(R) gravity theories which reproduce the cosmic acceleration, needs screening mechanism(i.e. Chameleon mechanism) to evade the solar system constraints. Then we argue that this screening mechanism, introduces new probes, which potentially can be used to distinguish this models from concordance model or Dark energy theories. This probes caused to enhanced gravity force in low density environments. For  this, we propose that dwarf galaxies could be a plausible low density environments(in comparison to Milky way) to detect deviations from GR. Finally we introduce a new parameter, known as environmental parameter, and assert that we can find some MG effects in kinematics of dwarf galaxies. Although there are large uncertainties on astrophysical effects which produce scaling relations in galaxies(i.e. fundamental plane), we propose that viable f(R) models may predict some detectable cosmological origin deviations in standard scaling relations.