Sleeping in Orbit

During his Huginn mission, ESA astronaut Andreas Mogensen performed the Sleep In Orbit experiment to learn more about how astronauts sleep, using in-ear measurement devices, that measured his brain activity as he slept. 

Read more about the experiment here: https://www.esa.int/Science_Exploration/Human_and_Robotic_Exploration/A_good_night_s_sleep_in_orbit