Each day of the Games we will bring ten facts you may or may not know about the great sporting spectacle that is the Olympics. Today we have sparkling siblings in focus
In the pool tonight it's the final of the men's 200m butterfly, another event won in 2008 (and 2004) by Michael Phelps. This was also one of Mark Spitz's seven gold medals in 1972, but four years previously the young Spitz's gold rush came adrift in Mexico when he finished last - with a Briton, Welshman Martyn Woodroffe, taking the silver medal. Phelps - and Ryan Lochte, the man shaping up to be the swimmer of London 2012 - also took gold in the 4x200m freestyle relay in Athens and Beijing (but look out for the French!).
After her astonishing victory in the 400m medley, all eyes will be on the young Chinese prodigy Ye Shiwen. She broke the pre-Games world record by over a second - and the bad news for the others is that the 200 medley is her preferred event! This was one of the golds won in 1996 by the controversial Irish swimmer Michelle Smith.
It's also the final of the women's 200m freestyle, won in 1996 by Claudia Poll, still Costa Rica's one and only Olympic gold medallist: eight years previously, her sister Silvia took silver, Costa Rica's first Olympic medal of any kind. Claudia just pipped the talented German Franziska van Almsick, who finished her career with ten Olympic medals, a record haul for anyone who never won a gold.
Basketball is in full flow at Olympic Park now: today's encounter between the United States and Tunisia sounds like a mismatch, but that's probably what people felt when the USA took on Puerto Rico in 2004 ... but they lost 92-73. The States also lost to Lithuania in Athens, and struggled to take the bronze medal. Argentina won gold that year, but the USA bounced back to collect the title for the 13th time out of 17 in Beijing.
At Lord's today the men's individual archery competition continues. The favourite is, astonishingly, legally blind: Im Dong-hyun of South Korea, a team gold medallist at the last two games, has 20/200 vision in his left eye and 20/100 in his right. Amazingly, he doesn't even use spectacles while competing: "I've practised using glasses before," he said at Lord's, "but actually it makes me feel less comfortable when I shoot."
Down in Dorset today sees the first outings for the men's and women's RS:X class - the discipline known to most people as sailboarding or windsurfing. The 1996 women's event produced a historic winner - Lee Lai Shan collected Hong Kong's one and only Olympic medal of any colour.
If you've been watching the sailing, and wondered what the Elliott class is all about, it's a rare example of an Olympic event being named after a person: the boats are six-metre yachts designed by the New Zealander Greg Elliott.
The Great Britain women's hockey team take on South Korea today in a repeat of the bronze-medal decider in Barcelona in 1992, which Britain edged 4-3. The first women's event at the Olympics, in Moscow in 1980, had surprise winners: Zimbabwe, captained by the sister of the future England Ashes-winning cricket coach Duncan Fletcher.
The eventing medals will be decided at Greenwich today. Britain has won three team golds and two individual ones - by Richard Meade in 1972 and Leslie Law in 2004. But if Australia win, it will be a fourth gold for Andrew Hoy, in his seventh Olympics. His wife Bettina was a team bronze medallist in 1984 - representing Germany - and in 2004 lost the gold medal (to Law) after a technical infringement in the final show-jumping phase.
In fencing today it's the finals of the men's foil, an event won both before and after the Great War by the great Italian Nedo Nadi. In Antwerp in 1920 Nadi won five golds - uniquely, in all three team events (foil, epee and sabre), and also in the individual foil and sabre competitions. Britain's five medals in men's fencing - all silvers - have all come in the epee.