Kaley Cuoco has said her Big Bang Theory co-stars are slowly starting to say their goodbyes as the show prepares to end its 12-season run.

The 33-year-old actress has said it is tough preparing to bid farewell to a "group of people" who feel like family to her.

Taking to Instagram, Cuoco, who plays Penny in the popular show, paid tribute to her team, writing: "To a group of people who have been way more than a 'second team' to us for the last 12 years . They are family!

"Thank you for being the cast behind the scenes..slowly saying our goodbyes over the next few weeks and it isn't getting any easier."

The much-loved show's 12th and final season will premiere on September 24 on CBS, and its final episode will air in May 2019.

In a joint statement released last year, Warner Bros. Television, CBS and Chuck Lorre Productions said, "We are forever grateful to our fans for their support of The Big Bang Theory during the past twelve seasons."

By the time the series wraps up, the show will have aired 279 episodes, and will be the longest-running multi-camera series in television history.

The Big Bang Theory, which first premiered in 2007, has earned 52 Emmy nominations and 10 wins during its run.

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