This landmark two-volume set brings together the scientific contributions of Prof. Kannan M. Krishnan, covering over four decades of dedicated research in nanomagnetism, materials science, and biomedical engineering. Volume 1, Biomedical Nanomagnetics, chronicles the design, synthesis, and application of functionalized magnetic nanoparticles for imaging, diagnostics, and therapy. Bridging nanoscience and medicine, this volume introduces a comprehensive "materials-to medicine" framework with real-world clinical impact-covering magnetic particle imaging, magnetic hyperthermia, and targeted drug delivery. Volume 2, Solid-State Nanomagnetism, explores the physics of nanoscale magnetic materials, including thin films, patterned heterostructures, and spin-dependent phenomena. With detailed studies on exchange bias, domain wall dynamics, and artificial spin systems, this volume lays the foundation for next-generation spintronic devices and magnetic logic. Together, these volumes reflect a unified research philosophy: rigorous in fundamentals, interdisciplinary in scope, and translational in ambition. From quantum phenomena to clinical innovation, this collection serves as both a scientific archive and an inspirational guideline for the future of magnetism, materials, and medicine.