Despite the observational success of the standard model of cosmology,
present-day observations do not tightly constrain the nature of dark matter and
dark energy and modifications to the theory of general relativity. Here, we
will discuss some of the ongoing and upcoming surveys that will revolutionize
our understanding of the dark sector.Comment: 31 pages, 22 figures. Contribution to the 3rd Jos\'e Pl\'inio
Baptista School on Cosmology held in 2016 in Pedra Azul, Esp\'irito Santo,
Brazil. Version accepted for publication in Univers
