Why does each chemical element have its own unique spectral-line signature? How do emission- and absorption-line spectra work? This lecture is the second part of a two-part exploration of the interaction between matter and light, today discussing how the unique spectral-line signatures of atoms are a reflection of their internal electron energy-level structure. We will discuss energy level diagrams for atoms, excitation, de-excitation, and ionization, and do a short demonstration with gas-discharge tubes and slide-mounted diffraction gratings. For podcast listeners, the last portion of the class is the demo, which we do not, unfortunately, have the resources to videotape. Recorded 2006 Oct 26 in 100 Stillman Hall on the Columbus campus of The Ohio State University.