  They are weak, they are small, and they are often overlooked, but they are
numerous and an ubiquitous sign of accreting black holes: compact radio cores
and jets in low-power AGN. Here I summarize our work concerning these radio
cores and jets in recent years, specifically focusing on the large population
of low-luminosity AGN. Special attention is also given to Sgr A*, the
supermassive black hole candidate at the Galactic Center, whose radio
properties are reviewed in more detail. This source exhibits a submm-bump,
possibly from an ultra-compact region around the black hole which should allow
imaging of the event horizon of the black hole in the not too distant future. A
jet model is proposed which explains the basic feature of Sgr A*: its slightly
inverted radio spectrum, the submm-bump, the lack of extended emission, and the
X-ray emission. This model also works for famous sources like M81*, NGC4258, or
GRS1915+105 based on the argument that radio cores are jets whose emission can
be scaled with the accretion power over many orders of magnitude. This scaling
is corroborated by the detection of many Sgr A*-like radio cores in nearby
Low-Luminosity AGN (LLAGN), some of which show jet structures on the VLBI (Very
Long Baseline Interferometry) scale. These cores confirm an AGN origin of about
half of the known low-luminosity AGN classified as LINERs and dwarf-Seyferts.
It is argued that in fact most of the compact radio emission at centimeter
waves in LLAGN is produced by a compact radio jet and not an Advection
Dominated Accretion Flow (ADAF). In general one can say that compact radio
cores are a genuine feature of AGN, allowing one to precisely pinpoint black
holes in many galaxies - not only in luminous quasars.
