A guided tour of the machine you live in — every major system and organ, one fascinating concept per card. Learn it to understand symptoms, follow your doctor, make better health choices, and appreciate the engineering keeping you alive right now.
You've lived in your body your whole life — but how well do you actually know it? It's a self-repairing, self-regulating machine of roughly **37 trillion cells**, running almost entirely on autopilot. Those cells organize into **systems**, each with a job: the heart and vessels **circulate**, the…