  Giant radio galaxies (GRGs), with linear sizes larger than 1 Mpc (H0=50
km/s/Mpc), represent the biggest single objects in the Universe. GRGs are rare
among the entire population of radio galaxies (RGs) and their physical
evolution is not well understood though for many years they have been of
special interest for several reasons. The lobes of radio sources can compress
cold gas clumps and trigger star or even dwarf galaxy formation, they can also
transport gas from a host galaxy to large distances and seed the IGM with
magnetic fields. Since GRGs have about 10 to 100 times larger sizes than normal
RGs, their influence on the ambient medium is correspondingly wider and is
pronounced on scales comparable to those of clusters of galaxies or larger.
Therefore `giants' could play an important role in the process of large-scale
structure formation in the Universe. Recently, thanks to the new all sky radio
surveys, significant progress in searching for new GRGs has been made.
