Jets in active galaxies are signatures of energy supply via collimatedbeams of plasma from the galactic nucleus to the extendedregions of emission. These jets, which occur acrossthe electromagnetic spectrum, are powered by supermassiveblack holes in the centres of the host galaxies. Jets are seenon the scale of parsecs in the nuclear regions to those whichpower the giant radio sources extending over several megaparsecs.These jets raise many challenging astrophysical questions.This article explores some aspects of jets in radio galaxiesand quasars, which are amongst the most powerful activegalaxies.