In the early 20th century, pregnancy testing required a slippery piece of equipment: a female African clawed frog. For decades, hospitals and research labs had a trusted supply of these handy creatures, employing their help in testing for pregnancy and in numerous other scientific endeavors. So what makes these frogs so special? Carly Anne York shares the secrets of these remarkable amphibians. Lesson by Carly Anne York, directed by Yajun Shi.