Life on Earth originated primarily from Carbon, Hydrogen, Nitrogen (along with Oxygen, Phosphorus, and Sulphur — often remembered as CHNOPS). Carbon is the backbone of all organic molecules. Hydrogen is essential for organic chemistry. Nitrogen is key for amino acids and nucleic acids. The Miller-Urey experiment showed that organic compounds could form from CH4, NH3, H2O, and H2 — all containing C, H, and N.