Allyson Felix won her second Olympic gold medal of the games and added a world record on top as she powered the US sprint relay team past their Jamaican rivals in the 4x100 metres last night.
The 200 metre champion ran a blistering second leg and 100 silver medallist Camelita Jeter finished off the world record job, pointing to the time clock with her mouth wide open as soon as she got past the line, seeing that the 27-year-old mark of the former East Germany was gone.
The US team finished in 40.82 seconds, shaving a massive 0.55 seconds off the old mark.
The rest of the American team was made up of Tianna Madison, and Bianca Knight.
Shelly-Ann Fraser-Pryce, Sherone Simpson, Veronica Campbell-Brown and Kerron Stewart won silver for Jamaica in 41.41.
Olesya Povh, Hrystyna Stuy, Mariya Ryemyen and Elizaveta Bryzgina combined to finish third for Ukraine and claim bronze.
Elsewhere last night, Ethiopian Meseret Defar deprived her teammate and arch-rival Tirunesh Dibaba an Olympic double for a second time when she produced a last gap sprint to claim victory in the 5000m.
Defar, who also won the 5000m at the Athens Games in 2004, timed a relatively slow 15 mins 04.25 secs, with world champion Vivian Cheruiyot of Kenya claiming silver in 15:04.73.
Defending Olympic champion and newly-crowned 10,000m gold medallist Dibaba, took bronze in 15:05.15.
Defar said: "It's a great day for me. Since 2008, I have tried everything as I wasn't able to win the Olympics.
"I have won two Olympic medals before and this is my third. I'm not sure I can do a fourth so this means a lot to me."
Defar waited on Dibaba's shoulder and pounced as her team-mate once known as the 'baby-faced assassin' flagged, looking for her trademark turn of speed for the line but coming up empty.
Asli Cakir Alptekin led a Turkish 1-2 when she held off Gamze Bulut to win the 1500m final after delivering a powerful final lap race.
Maryam Yusuf Jamal of Bahrain was third and American Morgan Uceny, who fell in the 2011 world championship final, tumbled again and beat the track in tearful frustration.
Russia's Tatyana Lysenko, who watched the 2008 Olympics on TV while serving a two-year doping ban, won the hammer gold with an Olympic record throw of 78.18 metres.
Lysenko, who won the world championship title last year, beat the old Olympic record of 76.34 set by Askana Miankova in Beijing with her first throw of the night, 77.56m, then improved it with her fifth.
Anita Wlodarczyk of Poland took silver with 77.60 and Germany's Betty Heidler finished with bronze.
The United States set the fastest time in qualifying for tonight's 4x400m relay final.
The quartet of Keshia Baker, Francena McCorory, Diamond Dixon and DeeDee Trotter won the second heat in a time of 3 mins 22.09 secs to cement their status as favourites to take the gold.
With 400m champion Sanya Richards-Ross expected to be part of the team today, Trotter believed they can go even quicker.
She said: "We have some tough legs tomorrow but we're going after some records."
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