A Florida couple is celebrating the homecoming of their baby boy who was born a 1-pound micro-preemie after he spent more than 100 days in the NICU.

Finn James Hill, lovingly nicknamed "Fighting Finn," was released from Nemours Children's Hospital in Orlando Sept. 10.

At birth, doctors gave Finn a 50% chance of survival.

"It didn't hit me until we left and it was the three of us for the first time," mom Jessica Hill of Lakeland, told "Good Morning America." "I knew we wouldn't have to take him back. It was everything we hoped and prayed for."

Jessica and Chris Hill experienced nine years of infertility. The couple underwent cycles of IVF with their own sperm and egg. After no success, the Hills looked into embryo adoptions.

Jessica Hill said she met a couple on Facebook, and through them adopted eight embryos. After one unsuccessful embryo pregnancy, Hill she became pregnant with twins.

At 10 weeks, she lost baby B. Baby A, Finn, survived. But Hill experienced a blood clot that caused her water to break at 24 weeks.

"Initially, it was just shock," Hill said. "I started crying and asking my doctor, 'What are his chances of survival if you take him out now?' The doctor said he was safer on the outside than he was inside."

On May 21, Finn was born via an emergency cesarean section. His original due date was Sept. 6.

On June 6, Finn was transferred from Lakeland Regional Medical Center to Nemours' level 4 NICU.

"I felt a little bit like a failure to be honest because one second he's inside of [me] and I'm protecting him, and the next he's out and in a complete separate part of the hospital," Hill recalled. "It was terrifying."

For the next few months, Finn relied on a ventilator and underwent surgeries -- one to repair a hole in his heart and another to correct Necrotizing enterocolitis, or NEC, a serious illness that affects a preemie's intestines, according to Stanford Children's Health.

Finn's health improved after his heart surgery, which improved lung function, Hill said.

And on June 30, one month after he was born, Hill got to hold her son for the very first time.

"It was unbelievable," Hill said when asked to describe the moment. "You only get to hold their hands, and I had to make due as far as touch goes, but it was a huge relief to watch his stats improve [as I did] skin-to-skin with him. It made me feel like my mom duties were kicking in and he knew who I was."

On Aug. 19, Finn was photographed by family friend Lindsey Cassidy in the hospital, where he spent his first four months fighting for his life.

Two weeks later, Finn's parents brought him home. He is now 4 months old and weighs 5 pounds, 5 ounces.

"Meet this NICU patient affectionately known as 'Fighting Finn,'" Nemours Children's Hospital wrote on Facebook in July. "Our Neonatal Intensive Care Unit confirms that the name certainly fits! He was born at 24 weeks and continues to make a remarkable recovery!"

Hill said her son is a good sleeper and a joy to be around.

"He just always has this grin on his face. He is so loved, I can't even tell you," she said.

"We're grateful this couple gave us our family," Hill added of Finn's genetic parents. "There's not a better gift than you could give ... to give people the opportunity to be parents."

The Hills are documenting Finn's journey on a Facebook page called Fighting Finn.