Jimmy Fallon thinks becoming a father is the ''greatest thing'' that's ever happened to him.

The 43-year-old talk show host has daughters Winnie Rose, four, and Frances Cole, two, with his wife Nancy, and says he couldn't be happier with his life as a parent, as he says it's helped him ''realise what's important''.

He said: ''It's the greatest thing that has ever happened to me. You realise what's important in life. Every single day you realise there's a new cute thing they're doing or saying.''

And Jimmy can't get enough of taking snaps of his brood, despite knowing that he'll never show them to anyone because no-one ''cares''.

He added: ''They fill up my phone memory with photos. I'm just taking these pictures that no one else wants to see. No other stranger cares that your kid ate an artichoke, but you think it's the best story ever. No it's not. It's boring. It used to be pictures of me and my wife, or sunsets or brunch - now none of that. Now it's just kids. I've got thousands. You become the guy you said you wouldn't become: 'I'm not going to be that guy that tells stories about their kids,' but I am now.''

The 'Tonight Show' host can't believe how different his two tots are, as despite giving both children the same upbringing, they've become ''two totally different humans''.

Speaking to People magazine, Jimmy said: ''They're two totally different humans. They act different - we feed them the same food, we show them the same TV shows, we read them the same books and they're just different human beings. The four-year-old is very polite. The two-year-old, if I turn around for one second, she has two knives. She's a totally different child!''