The magnetic fields and magnetospheres of hot stars: observational evidences

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 talk I will review the observing tools and our current knowledge concerning the detection and 
characterisation of the magnetic fields and magnetospheres in hot stars.