The Extremes In Intra-Night Blazar Variability: The S4 0954+65 Case

We present results of optical observations of the extremely violently variable blazar S4 0954+65 on intra-night time scales. The object showed flux changes of up to 100% within a few hours. Time delays between optical bands, color changes and rms-flux relations are investigated and the results are discussed in terms of existing models of blazar variability.