Biomedical engineering stands at a unique intersection. It is the only engineering discipline that must simultaneously satisfy the laws of physics, the complexity of biology, the variability of human patients, the rigors of regulatory science, and the ethical imperative of primum non nocere first, do no harm. Unlike a bridge that fails under static load, a medical device that fails does so in contact with the most vulnerable members of our society: the sick, the anxious, the hopeful. This book exists because the author has witnessed a persistent gap in the education of biomedical engineers. Students emerge from their undergraduate curricula with fragmented knowledge: fluid mechanics here, electrophysiology there, materials science elsewhere. They can solve the Navier-Stokes equations for steady flow in a rigid tube, but they cannot explain why a patient with aortic stenosis becomes short of breath when walking up stairs. They can derive the Hodgkin-Huxley equations, but they cannot explain why deep brain stimulation at 130 Hz alleviates tremor while stimulation at 50 Hz does not. They can calculate the diffusion coefficient of a drug molecule, but they cannot explain why Doxil® has a different toxicity profile than free doxorubicin.