America's first lady Michelle Obama embraces astronaut Mark E Kelly, the husband of Democratic Congresswoman Gabrielle Giffords.
The politician was one of 13 people wounded on Saturday when a gunman went on the rampage in Arizona.
Another six - including a nine-year-old girl - were killed.
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On Wednesday Gabrielle opened her eyes for the first time following brain surgery.
And she was well enough to receive a 10-minute visit from President Barack Obama and his wife just before a memorial service for the victims, attended by 14,000 people in Tucson.
Speaking to the crowd, he departed from his prepared text to announce the news.
There were cheers and whoops as the openly emotional US leader told them: "Gabby opened her eyes. So I can tell you she knows we are here. She knows we love her.
"And she knows that we are rooting for her through what is undoubtedly going to be a difficult journey," he said.
His tribute to Christina Taylor Green, the nine-year-old who died in the shooting, was particularly touching.
"Christina was given to us on September 11th, 2001, one of 50 babies born that day to be pictured in a book called 'Faces of Hope'.
"On either side of her photo in that book were simple wishes for a child's life. 'I hope you help those in need,' read one.
"'I hope you know all of the words to the National Anthem and sing it with your hand over your heart. I hope you jump in rain puddles.'
"If there are rain puddles in heaven, Christina is jumping in them today."
He ended by sharing his hope that the death of Christina, who had shown an early interest in public service, would unite the country.
"I want our democracy to be as good as she imagined it".