  Strong advances in direct evidence of magnetic fields in hot massive stars
have been possible thanks to the new generation of high-resolution
spectropolarimeters such as ESPaDOnS (on the Canada-France-Hawaii Telescope) or
HARPSpol (on the 3.6m ESO telescope). UV and optical high-resolution
spectroscopy has also been very useful to study the magnetospheres of massive
stars. In this contribution I review the observing tools and our current
knowledge concerning the detection and characterisation of the magnetic fields
and magnetospheres in hot stars.
