The intergalactic medium is probably filled with relativistic particles plasma and magnetic fields - just as frequently observed through the radio synchrotron emission from clusters of galaxies. The most promising mechanism responsible for the “enrichment” of groups are galaxies where bursts of star formation occurred. Such galaxies are frequently encountered in groups of galaxies, in particular in compact ones, where starbursts in two or more galaxies occur with short time intervals. This will lead to colliding galactic winds and to the amplification of magnetic field in the intra-group medium, as well as to shock heating of the thermal gas. With LOFAR, faint, diffuse synchrotron emission should be detected, possibly connecting the galaxies. Huge extensions which are rarely observed today (e.g. Figure 3) will be much more frequently seen in LOFAR’s radio maps.