Justin Bieber must know what he's missing, now that his ex-girlfriend Selena Gomez is coming into her own as a sexy young starlet.

Gomez, 20, strutted her stuff on the set of a music video shoot in Palmdale, Calif., on Monday. The singer/actress had several costume changes, including a retro red one-piece swimsuit paired with cat-eye sunglasses and multi-colored kitten heels.

Using a classic blue car in the background, she somehow even managed to make a yellow floral patterned oufit look sexy (see pics on the following pages).

Gomez's career is starting to take off. She stars in the upcoming film "Spring Breakers" (out March 22) in which she shares screen time with equally sexy stars Vanessa Hudgens, Ashley Benson and Rachel Korine. She is also working on a new album.

We predict a bright future for this former Disney star.

Check out more sexy shots of Selena...