PITTSBURGH -- Twin sisters Danielle and Dagian Lee happily played just feet away from each other on Monday -- yet farther apart than the 2-year-olds had ever been in their lives.

The little girls from Cleveland are finally on their own, after being born conjoined and later separated by surgeons at Children's Hospital of Pittsburgh.

"They did share a very large surface area, so when they were separated, essentially half of their torso and pelvis was open," said Dr. Joseph Losee, chief of the hospital's pediatric plastic surgery department.

Born in 2006, the girls were conjoined from the breast bone to the groin. They shared a third leg and many organs.

"They each had their own liver but it was fused in the middle by a pretty broad section, probably the size of my fist," said Dr. Timothy Kane, part of a team of more than 50 doctors and nurses that has been treating the Lees. "They had only one colon. They each had their own stomach, small intestine."

The medical team spent 24 hours in surgery in December, separating and reconstructing Catherine Nickson's young daughters.

"It was the longest day in the world," Nickson said.

The surgery -- "their birthday present," as Nickson called it -- began one day before Danielle and Dagian would each turn 2.

Mom also got a gift, one she only dreamed was possible, when the first-ever surgery of its kind at Children's turned out to be a success.

"There's probably been only 20 in the world of this type that have been separated, so it's something that none of us will probably ever do again," Kane said.

The girls have undergone several follow-up procedures. They'll have one more procedure -- a skin graft -- before transferring to a rehabilitation facility, WTAE Channel 4's Marcie Cipriani reported.

Nickson said she's so moved by this entire experience with her daughters that she has decided to attend nursing school.

"I think they're happier because they can actually go to sleep without somebody punching them in the face," Nickson said. "I think they're happy to get away from each other."