Listen to lecture note readings of scientific concepts from college-level courses while you sleep. From microbiology to astrophysics, you are sure to find a topic to learn about as you snooze. I used to record myself reading my college lecture notes as a way to study. I would play the recordings as I went to bed, when I brushed my teeth, while driving, and while walking between classes. I am now sharing those recordings to help others study for their classes, fall asleep, or even just learn a new topic.