  Almost exactly 3 decades ago, in the fall of 1986, the era of experimental
ultra-relativistic (\emph{E/m $\gg 1$}) heavy ion physics started
simultaneously at the SPS at CERN and the AGS at Brookhaven with first beams of
light Oxygen ions at fixed target energies of 200 GeV/A and 14.6 GeV/A,
respectively. The event was announced by CERN \cite{cernpress1,cernpress2} with
the usual superlatives "Break new ground.., World Record Energy ..", but also
with the information that "up to 400 particles were created per collision" and
that "over 300 physicists .. analyzing the data .. [try] to find out whether
the famous quark-gluon plasma really has been achieved". One would have thought
that with almost one physicist per particle, this would have been figured out
rather quickly. However, as we know today, 30 years and 21 Quark Matter
conferences later, the study of dense and hot matter, of the strong interaction
in the non-perturbative regime, has been a long and winding road. The journey
was much more difficult and time consuming, but also much more interesting and
rewarding, than anyone could have anticipated, with many twists, some dead
ends, and a never-ending string of surprises. This $30^{th}$ anniversary of
heavy ion physics, and the start of the 26$^{th}$ Quark Matter in Chicago, is a
good opportunity to look back and mention a few of the major results from each
of the three eras (fixed target/RHIC/LHC), along with some of the answers they
have provided us and some of the key questions which remain to be solved.

High Energy Physics - Experiment;Nuclear Experiment