It was 1990 when a third-year student, who had rocketed to the top at Harvard Law School, presided over a rally. He was a man making a mark.
"Well I had had about 5,000 law students by the time I met Barack Obama, the most impressive student I'd ever worked with," said Laurence Tribe, professor of constitutional law at Harvard Law School. "And now that I've had another 5,000 in the years since, so that remains true. I wrote his name on my desk calendar, which I don't very often do."
Obama took out student loans to pay his tuition and went on to graduate magna cum laude, earning a coveted spot on the Harvard Law Review, where a fierce political tug of war over vision and values was going on between conservatives and liberals.
Brad Berenson, a conservative Republican, said he wanted Obama to become president of the review because he had an unusual gift for finding common ground.
"I've worked at the Supreme Court, I've worked at the White House and I've never seen politics as personal or bitter as those on the Harvard Review," he said.
"The conservatives, as a whole in the end voted for Barack," Berenson said. "I think because they trusted him more to be fair and to be respectful to points of view different from his."
When Obama won that position, a ceiling shattered at the 173-year-old cathedral of American learning. At 28 years old, he appeared on local television, saying there was more that had to be done.
"For a lot of kids, the doors that have been opened to me aren't open to them," he said then.
"He had no interest in learning law just as a kind of intellectual exercise," Tribe said. "He needed to learn law to help people. He wanted to understand how the Constitution worked."
Back then Obama was already showing his signature combination of confidence and mystery.
"You do not get to be the Democratic nominee for president of the United Stated at age 46, now 47, if you do not have an enormous amount of self-confidence," Jon Meacham of Newsweek magazine said. "And that had to come from somewhere. Where'd it come from?"
Obama's mother, Ann Dunham, who earned a doctoral degree in anthropology and had a mission to give Third World women economic independence, was 17 when, in a Russian language class at the University of Hawaii, she met and fell for a brilliant student of economics.
He was 6 foot 1 and living a bare-bones existence at the YMCA. His name was Barack Obama -- and he was 23.
Neil Abercrombie was a classmate of Obama's mother and father in Hawaii.
"I see his dark glasses and a pipe and clenched in his teeth with a big smile on his face, and his joy in life. That's how I picture him," the congressman said of Obama's father.
"He thought he was the smartest guy in the room, I think," he said, laughing. "And with good reason. And everybody else thought so, too."
The young couple married, but the relationship ended when the elder Barack Obama accepted a scholarship to Harvard, leaving behind his 2-year-old son and his wife.
"She loved him," said Maya Soetoro-Ng, Obama's half-sister. "I mean, you know, I don't mean just a little bit."
Soetoro-Ng said their mother's legacy was to work hard and make the world a better place.
"She did wake us up in the middle of the night to look at the moon," she said, "which, was, of course, very frustrating. We just wanted to sleep."
But eventually his mother, too, would travel, leaving her son behind -- an absence that hurt more than he said.
"I think in retrospect, it was probably harder on me than I cared to admit," Obama told ABC News' Diane Sawyer. "You know, if you're a young boy or a teenager, you don't want to think that you still need your mom around."
"He wrote beautiful letters to her," Soetoro-Ng said of her older brother. "Sometimes in the corners, he would put little illustrations, little cartoon characters of himself, looking very cool."
Obama was 10 years old when he moved in with his two middle-American grandparents who would raise him and become the stable center of his life.
Looking at a photo, Obama said he saw the joy of his early childhood. Both grandparents came from Kansas. His grandfather was a World War II veteran who had come to Hawaii to find better work. Once there, their daughter threw them a curve.
"They had to absorb an awful lot," Abercrombie said. "Put yourself back 50 years. 'Hi mom, hi dad. You know, guess who's coming to dinner, right?' It's not Sidney Poitier."
Nonetheless, Abercrombie said, the grandfather loved his little boy, Barry.
"His grandfather was the most wonderful guy who loved that little boy," Abercrombie said, "took him everywhere."
There wasn't much money. They all lived in a 950-square-foot apartment. His grandfather's effort to sell furniture, and later insurance, failed. Holding the family together was a 5-foot-3 woman they called "Toot."
"She never got a college education, but is one of the smartest people I know," Obama said of his grandmother, who in a man's world, worked her way up from secretary to bank vice president.
Obama said his iconic image of his grandmother was seeing her come home from work and trading her business outfit and girdle for a muumuu, some slippers and a drink and a cigarette.
"She's where I get my practical streak," he said. "That part of me that's hardheaded, I get from her. She's tough as nails."
Watch "Portrait of a President" for much more on Obama's life and influences, and to read about John McCain's years at the Naval Academy, click here.