  This survey offers an introductory tutorial for students of any age of the
currently thriving field of hadrochemistry. We discuss the different chemical
potentials, how the hadronic phase space is described and how one evaluates the
abundance of hadrons at time of hadronization. We show that a rather accurate
description of experimental data arises and we present results of fits to
hadron yields at SPS and RHIC. We show that introduction of chemical
non-equilibrium originating in a sudden hadronization of a QGP is favored
strongly at SPS and is presently also emerging at RHIC. The low chemical
freeze-out temperatures are consistent with the picture of single freeze-out
scenario (chemical and thermal freeze-out coincide).
