This special issue memorial volume is dedicated to the late Professor Jean Cleymans, who made a visible contribution to high-energy nuclear physics and the search for the primordial matter of quarks and gluons, called quark-gluon plasma (QGP). An extraordinary scientist, educator and motivator, Prof. Cleymans, is known for his fundamental contributions to describing the matter created in ultra-relativistic heavy-ion collisions for the creation of QGP in the laboratory, using a two-parameter statistical hadron resonance gas model, which accurately describes and predicts the abundance of different hadronic species and their transverse momentum distributions along with providing a robust confirmation of thermal and chemical equilibrium of the process of particle production. This memorial volume has scientific contributions from stalwarts in the field, who were extremely fortunate and privileged to have a Colleague and Collaborator like Prof. Cleymans.