By Chad Finn, Boston.com Staff

LONDON -- Welcome to Day 7 of competition, where there's a ton going on -- 12 sports will award medals Friday, including swimming, which takes the spotlight for one more day ...

Friday's must-see event: Michael Phelps will take aim at his 21st Olympic medal when he competes in the 100-meter butterfly, his final individual Olympic race presuming there's no change of heart about taking a shot at the 2016 Summer Games in Rio as a 31-year-old. Missy Franklin will be 21 when the next Summer Games roll around, and there's a good chance she'll be Phelps's successor as the biggest fish in the Olympic pond (or pool, I guess). At 17, she's already a star, effervescent and apparently immune to pressure, having won gold in the 100-meter backstroke and 4x200 freestyle relay here, and today she goes for another in the 200-meter backstroke. She'll be challenged in that event by Saunderstown, Rhode Island's Elizabeth Beisel, who had the fastest time in qualifying.

Also worth watching: Track and field gets underway, with two medals to be awarded (women's 10,000 meters, men's shot put), and several preliminaries, including the women's 100 meters featuring US gold hopeful Carmelita Jeter. And singles tennis semifinals begin early at Wimbledon, with high-profile matches featuring Roger Federer vs. Juan Martin del Potro, Novak Djokovic vs. Andy Murray, Maria Sharapova vs. Maria Kirelenko, and Serena Williams vs. Victoria Azarenka.

Thursday's big story: Where to begin? Kayla Harrison seems like a good place. The Judo gold medalist who trains out of Wakefield is being hailed for her courage -- and that has little to do with what she's accomplished in her sport. Harrison speaks openly about the years of sexual abuse she suffered. Thursday marked the culmination of an extraordinary turnaround in her life. “I still feel like it’s a dream,” said Harrison. “I’m Olympic champion.” Talk about extraordinary strength.

There was plenty more: Swimmer Michael Phelps won his 20th overall medal, 16th gold, and first individual gold here, beating silver-medalist Ryan Lochte in the 200-meter individual medley. Phelps became the first male swimmer to win an event over three consecutive Olympics.

Carmelo Anthony dropped 10 3s and scored 37 points as the US demolished Nigeria in men's basketball, 156-73. If you knew that Stephon Marbury held the previous US record for single-game scoring (31 vs. Spain in 2004), I'm guessing you're probably Stephon Marbury.

And in the marquee event of the day, Needham's Aly Raisman finished tied for third in the women's gymnastics individual all-around, but missed out on the bronze because of a tiebreaker. Her teammate, supercharged 16-year-old Gabby Douglas, took the gold and has the Corn Flakes box to prove it:

Tweet of the day: Look out London: Ryan Lochte is done for the meet, will not swim on medley relay Sat. And tomorrow is his birthday. -- @YahooForde (Yahoo! sports writer Pat Forde).

Mind the gap, and stick around for further updates.