Chibiusa (Rini) fell from the sky one day right on top of Usagi and Mamoru whoile they were about to kiss!

She is actually their future daughter from Crystal Tokyo in the 30th century. She went back in time to the 20th century to find the legendary Sailor Moon and the Imperial Silver Crystal (which disappeared into her body in the 30th century), so she could help restore Earth, which had almost been destroyed by the Black Moon family. Later on (in the S series) she is sent back by her parents to train to become a Sailor Soldier, and can now transform into Sailor Chibi-Moon (Sailor Mini-Moon in the English dub).

Although her powers are barely showing, she is destined to become as powerful as her mother, Neo Queen Serenity, and during the brief spell where she was corrupted by Wiseman and became Wicked Lady one could glimpse at some of her capabilities (although we don't know how much of them came from the Black Crystal). Ultimately she finds the missing Silver Crystal from the future within herself, and combines it's power with Sailor Moon's to defeat Wiseman at the end of Sailor Moon R.

She is followed everywhere by Luna-P, a floating Luna lookalike ball that allows her to communicate through time with Sailor Pluto, amongst other things. It can also be used to hypnotise and turn into almost any object she needs.

Arriving in the 20th century, she hypnotised Usagi's family into thinking she was Usagi's cousin, and infuriated her future mum further by claiming Mamoru for herself! Later on, during the SuperS series, she developed a special relationship with Helios (Pegasus), which may or may not develop further on when she grows a little.

While she can be typically childish and stubborn, at heart she is selfless, kind, trusting and wise beyond her years, and frequently tells Usagi theres no way she could be her mother!

She attends an elementary school which she becomes quite popular at, and generally makes friends very easily due to her trusting and outgoing personality.

In the 20th century she lives with Usagi and her family, posing as Usagi's cousin, and in the 30th century she lives in the palace at Crystal Tokyo with her parents, Neo Queen Serenity and King Endymion.