The Low Frequency Array (LOFAR) is a new generation radio telescope which will observe the low frequency sky with unprecedented resolution and sensitivity. ... Due to its polarisation features and its resolution and large collecting area which provides unmatched sensitivities in the low radio waveband, LOFAR will be an extremely powerful instrument to study the Magnetic Universe. ... Astrophysical magnetic field science is one of the LOFAR Key Science projects. ...