Deisseroth (bioengineering and psychiatry, Stanford Univ.) is a pioneer in the field of optogenetics, the combination of genetic and optical methods to cause or inhibit well-defined events in specific cells of living tissues and behavior in animals. As a clinical psychiatrist, he is especially interested in using light to help decipher, and perhaps one day treat, the human brain. Here, he tells the stories of seven of his patients, including a young architect emotionally paralyzed by the death of his wife and unborn child in a car crash; a newly retired insurance executive who witnessed the 9/11 attacks; and an 84-year-old veteran with dementia who has suddenly stopped speaking. Deisseroth tells these stories from the patients’ perspective, as well as from his own, with endless patience, curiosity, creativity, and humanity. He believes that the evolving field of optogenetics has helped him understand his patients more deeply, and hopes that it will help treat people living with a variety of illnesses. VERDICT An engaging, accessible blend of psychology and science, which sets itself apart with Deisseroth’s lyrical writing and the empathy of his storytelling.