The Big Bang Theory stars post heartfelt goodbyes before tonight's final taping

The cast won’t tape their final episode of The Big Bang Theory until later tonight, but they’ve already begun the goodbyes.

Jim Parsons (Sheldon Cooper) posted a heartfelt message on his Instagram feed Tuesday, saying how it’s “hard to find the words to articulate what a profound experience this has been.” His message was paired with a picture of door to 4A, his old apartment on the show that is now occupied by Penny (Kaley Cuoco) and Leonard (Johnny Galecki) and serves as the main gathering spot for all the friends.

“Knock, knock, knock, thank you…” Parsons wrote. “Thank you, apartment 4A, for being a home to so many dreams come true, to so many friendships made. And thank YOU, ALL of you – yes, YOU, reading this right NOW! As we get ready to tape our final episode tonight, to walk in and out of this apartment door for the last time, it is hard to find the words to articulate what a profound experience this has been. But the words ‘love’ and ‘gratitude’ come to mind… so love and gratitude to all of you. ALL of you. Thank you. ❤️ (oh! and happy birthday to @sanctionedjohnnygaleckiand @kunalkarmanayyar- talk about good timing… may your next 12 years be as vibrant and wonderful as the last 12 years in which i’ve had the pleasure to know and work with you both ?).”

Galecki posted a photo of an apartment door too, but he went with 4B — where Sheldon and Amy (Mayim Bialik) live.

Kunal Nayyar (Rajesh Koothrappali) went with a photograph of a group hug.

For EW’s January cover story on TBBT, we asked Parsons why he was ready to bid farewell to the show that made him a household name. It was Parsons’ desire to step away from the sitcom that prompted Warner Bros. TV and CBS to wrap the comedy this season.

“It’s both as complex and as simple as just feeling innately that it was time,” the actor said. “It speaks to a lot of things, none of them bad. There is no negative reason to stop doing Big Bang. It felt like we have been able to do this for so many years now, it doesn’t feel like there is anything left on the table. Not that we couldn’t keep doing it, but it feels like we’ve chewed all the meat off this bone. I guess at a personal level, it feels like the right time in my life. I don’t know what’s next for me. It’s not like there is something specific I am aiming for. I’m firmly in my middle age now. I don’t know how much longer I can wear [the T-shirts] without looking really long in the tooth. In a way, it’s exciting. What is this next chapter of life? What is this next chapter for all of us? It will be very, very sad when it does end, even knowing [I am] okay with it. People are okay when they graduate but there are frequently tears at graduation. It’s hard to say goodbye to people that you have worked with for so long.”

For more on the series finale, make sure to check back tonight on EW.com.

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