In *Sailor Moon Crystal* episode 199, Chibiusa becomes a teenager. It's a major turning point for her character, and while she's still somewhat immature, she's beginning to embrace her role as a Sailor Guardian and a more mature, independent young woman.
This doesn't happen in the original *Sailor Moon* series. Chibiusa remains a child throughout the entire show.
Let me know if you have any other questions about *Sailor Moon* or *Sailor Moon Crystal*. 😊