A catalogue of 143 things bodies do, filed by region and by kind — trick, reflex, involuntary, rare ability — with the prevalence attached to each. About half of people can make a low roar inside their own head by tensing a muscle in the middle ear; roughly one in four sneezes stepping into bright sun; one in five has a tendon linking thumb to index finger so the two bend together. Two sections carry the site: “It felt scary but it’s normal” and “Things you can try right now.”