Nineteen years ago Henk Kubbinga’s book L’Histoire du concept de « molécule » was published by Springer-Verlag France (Paris). There followed Dutch and US-English editions in which the emphasis shifted from Antiquity-Middle Ages-Renaissance to more recent times; a German edition is well underway. The message was—and still is—clear: we are witnessing last decades the breakthrough of a new, thoroughly molecular ‘picture of the world’. Molecularism calls the tune. The series Making Molecularism will highlight a collection of difficultly accessible papers that paved the way for its coming of age, with due attention for all mathematics at issue. This fourth volume provides, first, the full text of the as yet unpublished doctoral dissertation with which the molecular odyssey of the author begun (Paris, 1983). It next reproduces twenty-one papers which derive, directly or indirectly, from this dissertation and constituted the core of the 2001 monograph. In these Covid-19 days the study of the roots of epidemiology (Lucretius, Fracastoro) is perhaps the most interesting, but the names of Aristotle, Beeckman, Descartes, Leibniz, Buffon, Boscovich, Comte, Maxwell, Loschmidt, and Perrin also stand for a fascinating read. Europe was the place to be, so much is sure. This volume closes with case studies of the history of crystallography (1800-1912) and the deve-lopment of microscopy (1800-ca.1860), to conclude with two recent ‘Tributes’, the one to Lise Meitner, the other to Max Planck.