Her doctors call it a "major milestone" in her recovery.
"We're hoping that she crosses through many more," said her neurosurgeon, Dr. Michael Lemole.
Her remarkable recovery five days after being shot through the head has provided a much-needed dose of jubilation after a tragic week that left the nation in mourning.
Giffords and 18 others were shot Saturday when a gunman opened fire at a meet-and-greet she was hosting outside a supermarket in her own hometown. Six people died, including a 9-year-old girl whose funeral was Thursday.
The three-term Democrat first opened her eyes on her own Wednesday evening while surrounded by her husband, astronaut Mark Kelly, and close friends from Congress.
Her left eye, which was unbandaged, started to flicker and she struggled a bit to widen it.
"Gabby, open your eyes, open your eyes," her husband urged her.
Kelly told her to give him a thumbs-up if she could hear him. She did more than that. She slowly raised her left arm.
President Barack Obama, who had just left her bedside to speak at a tribute for the shooting victims, announced the news to the thousands gathered in the University of Arizona arena -- and to the world.
The arena erupted in thunderous applause. There were tears. And hugs.
First lady Michelle Obama embraced Kelly, sitting beside her.
Giffords' movements left her friends astonished.
"It felt like we were watching a miracle," said Rep. Debbie Wasserman Schultz, who was at the bedside. "The strength that you could see flowing out of her, it was like she was trying to will her eyes open."
At a news conference Thursday at Tucson's University Medical Center, Lemole smiled when asked if it was a miracle. Then, he spoke carefully, as those trained to operate on the most delicate of organs do. He knows all too well the setbacks that could lurk.
"Miracles happen everyday," he said. "In medicine, we like to very much attribute them to either what we do or others do around us. But a lot of medicine is outside of our control and we're wise to acknowledge miracles."
He called her movements a "leap forward." Her doctors said her progress was not completely unexpected, but still remarkable.
Giffords was still in critical condition, with part of her skull removed to allow for brain swelling.
Few people survive a bullet to the brain -- just than 10 percent -- and some who do end up in a vegetative state.
The fact that Giffords is alert and moving "puts her in the exceptional category," Lemole said.
The doctors figured Giffords would open her eyes soon enough and were pleased that it coincided with Obama's visit. She can now keep them open for up to 15 minutes at a time.
Trauma chief Dr. Peter Rhee said Giffords acts like a bleary-eyed person just waking up.
Giffords yawns, rubs her eyes and tries to focus, he said. Doctors don't yet know if she can recognize her surroundings, but there are signs her eyes are beginning to track movements.
She is receiving physical therapy, which includes dangling her legs from her bed while propped up by nurses. Doctors hope to have her sit in a chair by Friday.
They also hope to remove her breathing tube -- what they called the next milestone.
Kelly has remained by her side the whole time, doctors said. He is scheduled to command NASA's last space shuttle flight, but that's uncertain now. NASA announced a fill-in commander Thursday just in case.
The latest progress is a far cry from last week, when a shocked nation braced for the worst, holding candlelight vigils outside the hospital and Giffords' Tucson office.
But as the days ticked by, doctors shared signs of improvement. There was a glimmer of hope early on: Giffords was able to squeeze a doctor's hand in the emergency room.
Giffords survived the gunshot wound for many reasons. The path of the bullet, quick and quality medical care, and a stroke of luck meant the difference between life and death, say her doctors and brain experts.
Doctors think the bullet pierced the front of Giffords' head and exited the back, slicing the left side of the brain, which controls speech abilities and muscles on the right side of the body.
They did not explain why her right eye was bandaged.
Had the bullet damaged both sides of the brain or struck the brain stem, which connects to the spinal cord, the outcome would likely be worse -- extensive permanent damage, vegetative state or death.
"So far, she's passed with flying colors of each stage" of her recovery, said neurologist Dr. Marc Nuwer of the University of California, Los Angeles, who is not involved in the congresswoman's treatment.
It is too early to tell the extent of damage, but experts say it is rare for people with gunshot wounds to the head to regain all of their abilities.
Damage to the brain's left side can result in memory loss, difficulty reading and hand-eye coordination problems. Her doctors have not been able to determine whether Giffords can speak, since she still has a breathing tube.
"Her full-time job now for the next year is working on her recovery and rebuilding her life around her disability, whatever it may be," said Dr. Stephan Mayer, professor of clinical neurology at Columbia University Medical Center in New York, who has no role in Giffords' care.
(Copyright 2011 by The Associated Press. All Rights Reserved.)