In this episode we talk about astrochemistry, which began in the 20th century. The first detection of molecules outside our solar system began with Theodore Dunham, which was finally recognized as a molecule in 1940. We talk of Gerhard Herzberg, Polydore Swings, and Dirk ter Haar, then meet Lyman Spitzer. Radio astronomy then became important in the 1960s and 1970s, allowing astrochemists to identify molecules based on quantum transitions at longer and longer wavelengths. We discuss the limited number of important elements for astrochemistry; the ever-growing number, size, and complexity of interstellar molecules detected, some ways they are formed, and end with some planetary chemistry.