Shonda Rhimes doesn't know how Grey's Anatomy will end.

The 55-year-old screenwriter has served as the show's executive producer since 2005 - but Shonda still doesn't know how the long-running TV show will conclude.

During an appearance on the Today show, Shonda explained: "To be at 450 [episodes] is amazing, and really all because of the fans and the fact that they've kept watching the show and they've stuck with it and they're excited and invested."

Shonda has been inundated with questions about the show's long-term future over recent years. But the acclaimed screenwriter doesn't know what the future holds.

She shared: "I'd say back at around episode 150, I knew how it was going to end. Now we're at 450, I have no idea. I mean, I wasn't sure we would get past season 4 or 5, so the fact that we're here in season 22 is insane."

Shonda also suggested that the show's future will be decided by the fans.

Asked how many more seasons there could be, Rhimes replied: "I feel like at this point, that decision is not mine as much as it is the fans … I want everybody to end in a really positive, great way."

Meanwhile, Shonda previously claimed that the TV industry faces a "very uncertain" future.

The screenwriter expects the "landscape" of the TV industry to change markedly in the coming years.

Shonda - who has her own production company called Shondaland - told Variety: "It's a completely different landscape, a completely different landscape. And I feel like when I look forward, I have no idea. It's very clear to me that my children only want to watch things that are this long because of YouTube or whatever.

"Sitting down and watching a movie is very rare for them. It's not the same as it was for us. Everything's changing. I think there will always be storytelling; I just don't know what form it's going to take."

Shonda isn't excited about where the industry is going.

She explained: "It's very uncertain, you know? I feel like if I was a television writer coming out right now, I would be a little bit more afraid. When I came out, it was the boom - it was the year the boom started. Now we're in the place where the bust is starting. So who knows?"