The quarterfinals kicked off at the US Open on Tuesday, with Li Na the first quarterfinal winner.
Li beat Ekaterina Makarova in three sets to reach the semifinals of the US Open for the first time.
Tuesday night saw Serena Williams reach the semifinals, beating Carla Suárez Navarro in straights.
And the stars were out on Arthur Ashe Stadium too, including David Schwimmer of Friends fame.
Also among the celebs in the stands were famous actors Lukas Haas and Leonardo DiCaprio.
Star Jones, a TV personality best known for her spot on The View, also caught the action.
Gabriel Macht, who stars as Harvey Specter in the fantastic show Suits, was also at the tennis.
Wednesday's first match saw Flavia Pennetta win an all-Italian quarterfinal against Roberta Vinci.
And at night, Victoria Azarenka rounded out the final four by defeating Daniela Hantuchova.
American author, journalist and talk show host Katie Couric watched the second day of quarterfinals.
Famous teenaged actress Dakota Fanning watched Wednesday's night session at Arthur Ashe Stadium.
Michael Strahan, an ex-football player and now co-host of Live! With Kelly And Michael, was there.
Donald Trump, real estate mogul and star of The Apprentice, with wife Melania in the stands.
And Jessica Biel, famous actress and wife of tennis fan Justin Timberlake, was also there.
Daylight faded on the US Open, and the four semifinalists would begin preparing for Friday...