Biden was transferred Tuesday evening to the Thomas Jefferson University Hospital in Philadelphia for observation and tests, following his morning check-in to a Delaware hospital.
He is in good spirits and talking with his family, according to a statement from his doctors.
For the Bidens, who have a family history of vascular problems, it was a real scare.
It's difficult to say whether family medical history played any part in Beau Biden's stroke and what the cause could have been, said ABC News' Dr. Richard Besser, but strokes are more common in young adults than people may think.
An estimated 10 to 15 percent of strokes -- most of them ischemic or due to blood clots, rather than hemorrhaging -- occur in people under 45.
In the elderly, strokes are normally caused by the hardening of arteries and plaque that goes to the brain. In young people, the reason is usually a defect in the heart or a tear in an artery that causes a clot, which can go to the brain and cause a stroke, Besser said on "Good Morning America."
Biden likely didn't have an aneurysm, like his father.
"If you have an aneurysm and it ruptures, causes bleeding, that can cause a stroke," Besser said. "But you wouldn't expect a rapid recovery like we're hearing about here," Besser said.
There are three key symptoms of a stroke -- facial drooping, lack of ability to lift arms and slurred speech. Besser said if people experience any one of the three, they should immediately go to the hospital. Similarly, severe headaches can also be dangerous.
If you have the "worst headache of your life, be seen," Besser said. "Or if you have a headache that has any tingling or any neurological signs in your body, be seen right away."
Doctors say the next step is to conduct more diagnostic tests to determine what caused Biden's stroke, in order to prevent it from happening again.
Biden, who was elected as Delaware's attorney general in 2006, is physically fit. He recently served in Iraq for one year as a captain with the Delaware Army National Guard.
But doctors say fitness and youth are no guarantee against strokes, the third leading cause of death in the United States, behind heart disease and cancer.
Young men over the age of 30 are more prone to strokes than women, who are more vulnerable under 30. African Americans are also more likely to suffer a stroke at a young age.
Stroke kills about 137,000 Americans a year, according to the Centers for Disease Control and Prevention. It is also the leading cause of disability.
More than 700,000 Americans, some of them young and seemingly healthy, have a stroke each year; women have about 55,000 more than men.
Because less is known about this disease among young people, the American Academy of Neurology has just received a grant to study stroke in that population, according to Dr. Aneesh Singhal, associate professor of neurology at Harvard Medical School, who practices at Massachusetts General Hospital in Boston.