Two Japanese researchers have revealed the first details of their claim to have grown tadpole eyeballs from scratch in the lab. They say the eyes are functional when they transplanted into tadpoles, and even work when the tadpoles metamorphose into frogs.

“None of the eyes were rejected and none dropped out,” said Makoto Asashima, of the University of Tokyo. “All of the frogs can see.”

Asashima and colleague Ayako Sedohara say it is the first successful transplantation of an eyeball grown in a test tube into a living animal.