Q: What is the human body made of?
A: The human body is built from trillions of cells. Similar cells group into tissues (muscle, nerve, epithelial, connective). Tissues form organs (heart, lungs, brain), and organs work together as systems (circulatory, respiratory, nervous, etc.). Chemically, the body is ~60% water, along with proteins, fats (lipids), carbohydrates, and minerals such as calcium and iron. Inside cells, DNA stores instructions for building proteins. The microbiome (beneficial microbes in the gut, skin, and mouth) also supports digestion, immunity, and vitamin production. Health depends on these parts staying in balance—known as homeostasis—so that temperature, pH, and fluid levels remain stable.