Actress Mary-Kate Olsen is an American actress, fashion designer, producer, and author. She began her acting career at the age of nine months, appearing in the television series Full House. She is best known for her role as Michelle Tanner on the show, which she shared with her twin sister Ashley Olsen. Mary-Kate has also starred in several films, including It Takes Two, New York Minute, and The Challenge. She has also released several books and launched a successful fashion line.