We discuss all-optical interrogation techniques and the mysterious claustrum. Paula Kaanders and Lukas Krone talk to Dr Adam Packer from the Department of Physiology, Anatomy & Genetics about his work on all-optical interrogation techniques: a technology that enables him to read and write neural activity. Besides this, we talk about his recent interest in the claustrum, a brain region we know little about. Adam also discusses his career path and his advice to graduate students.