Abstract
Active Galactic Nuclei (AGNs) have an extreme behavior at almost all wavelengths. In particular, the kind of AGNs know as blazars are one of the most extreme. With their jets pointing near to our direction, those object show a variety of distinctive features from radio to very high energies. We present the results of an extended campaign to study the behavior of the optical emission of blazars. This work is centered on variability at short scales of total flux. We took special care in data treatment, e.g. considering the influence of the host galaxies, the good choice of the field stars used for differential photometry, the statistical test used to study the variability, etc. Over the last years, we followed blazars that were detected at very high energies (TeV). We found differences in the incidence of variability at short time-scales between blazars that have the peak of their synchrotron flux low frequencies from those that have it at high energies.
