Reese Witherspoon recounts filming her 1st movie and what she wore to her 1st premiere

To celebrate her 30th anniversary of breaking into Hollywood, Reese Witherspoon treated fans to an exclusive story about how she got her start in the movie industry.

The 43-year-old posted an intimate four-minute Instagram video with the caption, "Let me tell you a story of how I booked my first movie!"

She explains that she knew she wanted to act when she was very little, "which is kinda weird because both my mom and my dad were in the medical industry," she jokes.

After being cast in a local flower shop commercial, the young Witherspoon was bit by the acting bug and begged to take acting classes -- which she excitedly sat through for four hours every Saturday.

After booking a few more commercials, the "Legally Blonde" actress said her big break came when she read an ad in a paper that asked "Do you want to be in a movie?" The movie was asking for "a 14-year-old Southern girl," and as she fit the request, she auditioned.

She wound up being offered the role for "Man in the Moon." "It was the summer before the start of freshman year of high school and we shot all summer," reflects Witherspoon. "And it was the most magical experience."

Besides learning the ins and outs of acting, she also comically revealed that she had to learn how to run properly. "The director wanted me to be a tomboy and wanted me to run ... and the way I ran, he thought, wasn't very athletic," laughs Witherspoon.

While the movie wasn't a big success, the positive reviews she received propelled her career to where she is today.

She also recapped what she wore to her first movie premiere: A velvet dress "and cowboy boots ... 'cuz cowboy boots!"