  Relativistic jets in active galactic nuclei (AGN) are among the most powerful
astrophysical objects discovered to date. Indeed, jetted AGN studies have been
considered a prominent science case for SKA, and were included in several
different chapters of the previous SKA Science Book (Carilli & Rawlings 2004).
Most of the fundamental questions about the physics of relativistic jets still
remain unanswered, and await high-sensitivity radio instruments such as SKA to
solve them. These questions will be addressed specially through analysis of the
massive data sets arising from the deep, all-sky surveys (both total and
polarimetric flux) from SKA1. Wide-field very-long-baseline-interferometric
survey observations involving SKA1 will serve as a unique tool for
distinguishing between extragalactic relativistic jets and star forming
galaxies via brightness temperature measurements. Subsequent SKA1 studies of
relativistic jets at different resolutions will allow for unprecedented
cosmological studies of AGN jets up to the epoch of re-ionization, enabling
detailed characterization of the jet composition, magnetic field, particle
populations, and plasma properties on all scales. SKA will enable us to study
the dependence of jet power and star formation on other properties of the AGN
system. SKA1 will enable such studies for large samples of jets, while VLBI
observations involving SKA1 will provide the sensitivity for pc-scale imaging,
and SKA2 (with its extraordinary sensitivity and dynamic range) will allow us
for the first time to resolve and model the weakest radio structures in the
most powerful radio-loud AGN.
