When I started working on RR Lyrae atmospheres, and during a comparative study with Preston's spectroscopic works (1964 & 1965) on atmospheric phenomena, I unexpectedly found the existence of hypersonic shock waves (1996 & 2008) in the RR Lyrae atmospheres and how strongly they are connected with the turbulence amplification mechanism and the Blazhko modulation in the pulsation of RR Lyrae stars. Despite the fact that several authors claimed to detect a magnetic field, Preston (1967), deploying a lot of effort during two years, dis not detect any strong magnetic field. This is consistent with my recent spectro-polarimetric measurements (2004), during four years, leading to the falsification of all the models of the Blazhko effect requiring striong photospheric magnetic fields. I will talk about the observational background and new implications of spectroscopic works for explaining the interplay between atmosphere dynamics and pulsation, the Blazhko phenomenon and finally the long-term modulation of RR Lyrae stars.

Although the RR Lyrae stars have been studied for more than a century, they remain highly amazing targets to increase our understandig of stellar physics and we stress the need for additional efforts to exploit their full potential.