What Is Light? -- The Interaction Between Light and Matter -- Light Sources -- Examinations with Light -- Ultrasound Diagnostics -- Further Imaging Procedures -- Interventions with Laser Light -- Some History of Chemistry -- Oxygen -- Water -- Carbon Dioxide (CO2) -- Nitric Oxide -- Redox Reactions -- DNA -- RNA -- Proteins -- Lipids -- Matter: Using Water as an Example -- If You Are Interested in More ... -- Appendix: Units and Constants