  Statistical physics has proven to be a very fruitful framework to describe
phenomena outside the realm of traditional physics. The last years have
witnessed the attempt by physicists to study collective phenomena emerging from
the interactions of individuals as elementary units in social structures. Here
we review the state of the art by focusing on a wide list of topics ranging
from opinion, cultural and language dynamics to crowd behavior, hierarchy
formation, human dynamics, social spreading. We highlight the connections
between these problems and other, more traditional, topics of statistical
physics. We also emphasize the comparison of model results with empirical data
from social systems.
