This Special Issue will deal with pathophysiological as well as the phenomenological signs of insomnia. For example, Is 'hyperarousal' outdated? What is the difference between acute and chronic insomnia? What sleep disorders are linked to traumatic brain injuries? How is social facial recognition impacted by insomnia? What factors are linked to socioeconomic factors and alcohol consumption in the face of insomnia? We aim to set forward new thinking about insomnia research, including unchartered territories needing to be explored. Reviews, meta-analyses, and new experimental research are welcome in this Issue.