  We present a brief overview of a very extensive studies of the group of
active galactic nuclei (AGNs) that transitioned to radio-loud state over the
past few decades. The sample consists of twelve sources, both quasars and
galaxies, showing the characteristics of gigahertz-peaked spectrum (GPS)
objects undergoing relatively rapid changes, due to the evolution of their
newly-born radio jets. Discussed objects also show a wide range of physical
parameters such as bolometric luminosity, black hole mass and jet power,
suggesting a great diversity among young active galactic nuclei and their
hosts. Furthermore, we introduce a new observational project, the aim of which
will be to investigate and gain a more in-depth understanding of the phenomenon
of slow radio transients.
