  The unprecedented photometric precision along with the quasi-continuous
sampling provided by the Kepler space telescope revealed new and unpredicted
phenomena that reformed and invigorated RR Lyrae star research. The discovery
of period doubling and the wealth of low-amplitude modes enlightened the
complexity of the pulsation behavior and guided us towards nonlinear and
nonradial studies. Searching and providing theoretical explanation for these
newly found phenomena became a central question, as well as understanding their
connection to the oldest enigma of RR Lyrae stars, the Blazhko effect. We
attempt to summarize the highest impact RR Lyrae results based on or inspired
by the data of the Kepler space telescope both from the nominal and the K2
missions. Besides the three most intriguing topics, the period doubling, the
low-amplitude modes, and the Blazhko effect, we also discuss the challenges of
Kepler photometry that played a crucial role in the results. The secrets of
these amazing variables, uncovered by Kepler, keep the theoretical,
ground-based and space-based research inspired in the post-Kepler era, since
light variation of RR Lyrae stars is still not completely understood.
