Recent developments in CMB and large-scale galaxy surveys have led to the
standard cosmological model, but the physical understanding of its
ingredients remains elusive so far. In response to the gravity of these
issues, numerous large-scale galaxy surveys are ongoing or planned to be
operational in a near future. However, precision measurements in future
galaxy surveys bring in new challenges, demanding substantial advances
in theoretical modeling and observational methods. I will discuss the
recent theoretical development in modeling galaxy clustering in a relativistic
context and the observational issues associated with this recent development. 
The relativistic effect in galaxy clustering or the deviation from the 
standard Newtonian description becomes substantial on large scales, in which 
dark energy models or alternative theories of modified gravity deviate 
from general relativity, and in which the fingerprint of the inflationary 
epoch remains in its pristine form. I will discuss how the subtle relativistic 
effect in galaxy clustering can be used to test general relativity on large 
scales and probe signatures of the early Universe.