  TeV emission can be a common characteristic of low power blazars. This is in
line with the sequence of blazars relating the observed bolometric luminosity
with their overall spectral energy distribution. Detecting new TeV blazars,
possibly at different redshifts, is important for studying the particle
acceleration process operating in the jet, and it is even more important for
studying the far infrared-optical background. Recent studies of low power BL
Lacs suggest that the particle acceleration mechanism may be a two-step
process, analogous to what is invoked to explain the spectra of gamma-ray
bursts. I will briefly discuss these findings, together with a simple scheme
for selecting good TeV candidates and I will briefly comment on the very fast
TeV and X-ray variability observed in BL Lacs.

Astrophysics