Her doctors call it a "major milestone" in her recovery.
She 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.
Her doctors said her progress was not completely unexpected but still remarkable.
Giffords was still in critical condition.