There's some things you can never recreate in life. Hearing your baby's first words, watching them take their first steps, and watching them grow up, for example.
However, in some cases not all parents are lucky enough to see that. While some children never get to hear, speak or see, scientists are putting hours of research and experimentation to see if they can fix that.
That's why when there's some success with it, it's amazing.
Take this video. Michelle and Toby Lever were worried for their baby Lachlan after he was diagnosed with a hearing impairment in both ears. This meant that he may never be able to hear again and thus not be able to speak.
However he was given special hearing aids and you can see the moment when he finally hears his first words and his life changes.
"We were completely overwhelmed and so emotional when the hearing aids were turned on," Aussie mum Michelle told BBC News. "We were crying from happiness, our baby not only smiled for the first time but more importantly he heard. His whole world opened up.
"It was the most amazing thing we've ever seen in our lives."
Toby was also overcome with emotion because his son's future is now a lot more open, thanks to him now being able to develop linguistic skills.
"Lachlan is going to have to wear hearing aids for the rest of his life, unless there's going to be some research that comes about," Michelle continued.
The original video is now three years old, and Michelle is happy that Lachlan is able to live his life to the full.
He now absolutely loves music, and apparently tries to dance in the car whenever a song comes on.
Featured Image Credit: YouTube