The Big Bang Theory is ending because Jim Parsons "wanted to leave" the show.
It was announced this week that the hit US comedy show will be ending after its upcoming 12th season.
According to Entertainment Weekly, CBS was attempting to negotiate another two seasons with the stars but Parsons, who plays Dr Sheldon Cooper, wanted to leave the show, prompting Warner Brothers TV and CBS to end the popular sitcom.
Now, in an Instagram post, Parsons has said it's "nearly impossible" to accept the series is ending, writing: "I feel very fortunate that we have another 23 episodes to shoot this season because I am hopeful that with each and every one, my level of REALLY accepting this fact will sink in.
"Something else I feel grateful for - and this gratitude needs no time to 'sink in' or become more 'realized;' this grateful-feeling is always with me but is multiplied in this moment of us announcing our final season - but I feel such intense gratitude for our devoted viewers who are the ACTUAL reason we have been graced with the opportunity to explore these characters for 12 years of our lives."
He continued: "I feel grateful to our crew - many, many of who have been with us since day one - and who are the people who bring a sense of steadiness and dependability, who are so warm and king and always quick to say hello and smile at us every time we come to the set and who, even though you don't see them on TV, are in many ways the real and steady heartbeat that keeps this body of work alive and breathing while we, like flailing arms and legs, act like jackasses and fools in an attempt to make someone laugh.
"I am grateful to all the writers of our show - those with us now and those that have come and gone - because, without them, there would literally be no Big Bang Theory at all, ever. The writers thought of this show, the writers created these characters, the writers are the ones who found ways to keep coming up with organic, entertaining ways to keep the life of this show going which is a task much, much more challenging than anyone other than them will ever know or understand.
"And while I know that they already know it, it bears repeating again and again: I am so terribly grateful for the cast in this picture and the cast members who aren't pictured here - whether they were in one scene or many episodes along the way; you are all my playmates that I have fallen in love with and who have become a part of my life on set an off.
"You are my playmates when we don't feel like playing but have to because it's our job to get out there and communicate and pretend we're these other fictional people and we look into each other's eyes and say these words and end up creating this weird, other reality that has enriched my life more than I will fully ver understand."
He added: "I will miss all of you and all of this more than I can say and more than I can know at this time."
The CBS sitcom, which is the most watched television comedy in the world, will end its triumphant 12-season run as television's longest-running multi-camera comedy in history.
The Big Bang Theory's twelfth and final season will premiere on CBS in late September.