"This summer we welcomed our sweet baby girl through adoption. We are beyond excited to embark on this beautiful next chapter of parenthood in both peace and privacy," she wrote in the post.

Millie Bobby Brown has revealed she adopted a baby girl -- and fans are mind-blown that the young actress they watched grow up on Stranger Things is officially a mother.

“This summer we welcomed our sweet baby girl through adoption. We are beyond excited to embark on this beautiful next chapter of parenthood in both peace and privacy,” the Instagram post reads.