Hearing a child's first word is one of the most precious moments of being a parent.
But for Toni and Paul McCann the event was even more special because their son Cillian has just said 'hello' – at just seven weeks old!
The amazing moment was caught on camera by mum Toni, who shared it online for the world to witness.
In the 23 second clip - that has been viewed on YouTube more than 300,000 times - Toni is heard gently coaxing Cillian, repeatedly saying 'hello'.
He responds for a while with gurgles and the cute baby noises we've all come to expect from a happy youngster, before astonishing Toni by replying with a confident and very audible 'hello' in return.
Toni's surprised reaction can be heard briefly before the video abruptly ends.
Toni, from Finaghy, Northern Ireland, posted the clip to her Facebook page, prompting family and friends to call Cillian a 'little genius in the making'.
Within days the clip had been shared on social media and watched hundreds of thousands of times.
Toni and Paul recently celebrated their 13-year wedding anniversary and they couldn't have asked for a better present.
They told the Belfast Telegraph that they've been inundated with messages of people saying how amazing their child is.
Toni said:: "It's been mad. I've had messages from everyone."
When asked if Cillian had repeated his amazing feat, she said: "He hasn't said anything since but you can tell when he's trying. When he flicks his tongue in a certain way, you know he wants to say something."