  Cold, dense filaments, some appearing as infrared dark clouds, are the
nurseries of stars. Tremendous progress in terms of temperature, density
distribution and gas kinematics has been made in understanding the nature of
these filaments. However, very little is known about the role played by
magnetic fields in the evolution of these filaments. Here, I summarize the
recent observational efforts and ongoing projects (POLSTAR survey) in this
direction.
