Just like he did four years ago, Miles Fawcett is there to catch his daughter when she needs him.

Serena was born with a severe liver defect. Her dad donated part of his liver to save his little girl's life. Now both have what's called a pre-exisiting condition.

The Affordable Health Care law says no insurance company can deny coverage based on that. Serena's mother, Mira, worries what might happen if the Supreme Court rules the law unconstitutional.

“It’s difficult for me to think about somebody who’s gone through something through no fault of their own, who’s had to go through so much, to have the bottom drop out like that," she said.

Steve Fleishman runs a bagel business and does not offer health care to every employee. He would see no change if he stays under 50 employees. But, if he hires more, Fleishman would have to offer affordable coverage to his regular workers or pay a penalty. 

He says - in this economy - there's not much profit left over when he wraps up the day, so, he'd have to raise prices and cut staff. 

“I’d want to fall into the category of somewhere between 40 and 49 employees, so somewhere along the line we’d have to trim down and work a little harder to not be in that category so we wouldn’t have to pay for health benefits," said Fleishman.

Dianna Buckett is studying for an advanced degree in public health at Johns Hopkins University. The new law allows her to remain under her parents' health insurance until age 26, even after graduation.

“There’s not a lot out there that’s a full-time position without prior job experience," said Buckett. "A lot of what I’m looking into is internships and, even if they are paid, the biggest thing is you don’t get benefits.” 

"On every scale this is a monumental case," said attorney Tom Goldstein.

Goldstein has a stash of quill pens - one to mark each case he's argued before the Supreme Court. The real debate here is if Congress has the authority to mandate health insurance for all Americans.

"It involves the signature accomplishment of the president and it involves a question which affects the healthcare, which is absolutely basic to a hundred million people at least," he said.

With that in mind, the justices have scheduled six hours of arguments over three days. That's the longest given any case since the 1960s. And for good reason - analysts say their decision will be cited in American courts for the next 250 years.