This book brings together a collection of essays dedicated to the memory of John L. Heilbron (1934–2023), one of the foremost historians of science of his generation. Originally conceived as a Festschrift to mark his 90th birthday, it became a memorial volume following his passing. The contributors — former students, colleagues, and collaborators — reflect the breadth of Heilbron’s scholarship, from the Scientific Revolution to modern physics, from Lamarck and Darwin to contemporary science writing. The essays exemplify his approach to the history of science: technically informed, contextually grounded, and attentive to language and method. Together, these studies trace the enduring influence of Heilbron’s work on the practice of historiography itself. They illustrate how his legacy continues to shape new research agendas, connecting detailed historical inquiry with broader questions about knowledge, culture, and scientific understanding. This volume is both a tribute and a continuation of his intellectual project.