When I started to learn physics, in mid-60's, the hottest issue was recently discovered spectroscopy of the ``elementary particles" and its apperent SU(3) symmetry. By the time of my Ph.D. (1974) the fundamental theory of strong interaction -- Quantum Cromodynamics (QCD) was discovered. Its perturbative part which is rather similar to Quantum Electrodynamics except the asymptotic freedom. I wandered whether finite QCD T matter is sreening or antiscreening: unlike the vacuum, it turned out the former is correct and Quark-Gluon Plasma (QGP) was named so in my 1978 paper However, the so called nonperturbative QCD turns out to be much more difficult to understand, and intence work in this direction is going on till today (including the ``lattice QCD" based on the most powerful computers).

In 1982 I have proposed the so called ``instanton liquid" model of the QCD vacuum, considering the ``vacuum" (the ground state) as an ensemble of interacting non-linear fluctuations called instantons. During 80-90's it was shown that this model not only reporduces some facts about the vacuum itself, but it also leads to very good spectra and other parameters of strongly interacting particles (e.g. nucleons and pions). Quark states bound to instantons - the so called zero modes -- were proven to form a kind of basis for most important quark states with near-zero Dirac eigenvalues, they play a role analogous to what states at the Fermi surface are for metals.

Another related direction of my studies is properties of matter which is so hot or dense, that ``elementary" particles are melted and qualitatively new phase of matter -- QGP -- appears. It took some time till those ideas propagated, then experimental program with heavy ion collisions have started in Brookhaven and CERN (Geneva). Signifcant hopes were raised due to construction of Relativistic Heavy Ion Collider (RHIC) in Brookhaven. It was completed in 2000 and alredy its maiden voyage in the summer of that year had not disappoined us! Indeed QGP was there, and it turned out to be a ``near-perfect liquid" behaving exactly as our hydrodynamical predictions (worked out by my graduate student Derek Teany). We had fun describing the so called radial, elliptic, and also new phenomenon predicted by us -- the conical flow from propagating jets, similar to sonic boom in air.

Theoretically to explain why QGP is in a strongly coupled liquid-like phase is very challanging. We now use methods ranging from classical molecular dynamics to string theory to model it.