1907–2007: What's new on the Blazhko front?

On the centenary of the discovery of the Blazhko effect [1], it is time to give a rundown of what progress has been made over the past decade in the understanding of the phenomenon. The Blazhko effect is a periodic amplitude and/or phase modulation of the light curve, shown by a large fraction of the astrophy sic ally important RR Lyrae stars. Despite numerous devoted observational studies and elaborate models attempting to reproduce the modulation, it still defies a definitive explanation. This paper attempts to give an overview of the observational and theoretical status of studies devoted to the phenomenon.