Polarimetry in the X-ray band is argued to be a powerful and sometimes
unique tool in diagnosing the magnetic field, geometry and emission
mechanism in astrophysics. PolarLight, which is a miniature X-ray
polarimeter onboard a CubeSat, is the first dedicated astronomical X-ray
polarimeter since the OSO-8 experiment in 1970s. It was launched into a
low-Earth orbit in October 2018 and is still working in space. In this
talk, I will introduce the PoarLight space program and the science
results that have been obtained with it.