The San Diego Zoo recently announced the first healthy clone of an endangered species, a Javan banteng. The clone is an early sign of success for the “frozen zoo” concept, where cells from endangered species are stored in hopes that cloned animals can be produced at a later time.

The process is still very inefficient, with 45 embryos and 30 cows required to give birth to a single banteng healthy enough to live past a few days. However, scientists at CRES are hoping that the process will provide greater genetic diversity to existing zoo populations.