The book gathers several contributions by historians of physics, philosophers of science and scientists as new essays in the history of physics ranging across the entire field, related in most instances to the works of Salvo D'Agostino (1921-2020), one of the field's most prominent scholars since the second half of the past century. A phenomenon is an observable measurable fact, including data modelling, assumptions/laws. A mechanical phenomenon is associated to equilibrium/motion. Are all mechanisms mechanisms of a phenomenon? Scholars with different backgrounds discuss mechanism/phenomena from an historical point of view. The book is also devoted to understanding of causations of disequilibrium (shock, gravitational, attraction/repulsion, inertia, entropy, etc.), including changes/interaction in the framework of irregular cases of modern physics as well. The book is an accessible avenue to understanding phenomena, ideas and mechanisms by leading authorities who offer much-needed historical insights into the field and on the relationship Physics-Mathematics. It provides an absorbing and revealing read for historians, philosophers and scientists alike.