Juvenile fillies are young female horses, typically under the age of two. They are often involved in horse racing and are classified as "juveniles" until they reach a certain age. These fillies are known for their speed and agility, making them exciting competitors on the racetrack. In the context of horse racing, juvenile fillies may participate in specific events, such as the Breeders' Cup Juvenile Fillies, which showcases the best young female horses. Training and care for these young horses are crucial, as they develop their skills and physical abilities during this formative stage of their lives.