Steroid hormone production peaks in the morning and dips to its lowest in the evening. Hannah Grotzinger et al. investigated how hormone fluctuations impact brain function by measuring testosterone and cortisol production and brain functional connectivity of a human male every 12 to 24 hours for 30 days. Changes in testosterone (Top) and cortisol (Bottom) were associated with significant alterations in the brain's functional network architecture. See the article by Grotzinger et al. for more information. Cover image: Hannah Grotzinger.