Sheldon (Jim Parsons) and Amy (Mayim Bialik) finally "got physical" in the Season 9 winter finale of "The Big Bang Theory." It was a big decision for the couple — Sheldon even needed some advice from guest star Bob Newhart dressed as Obi-Wan Kenobi! But Bialik says that behind the scenes, the show's writers and producers were equally careful about how they handled the delicate task of having "Shamy" lose their virginity on national TV.

In episode 11, "The Opening Night Excitation," it was Amy's birthday and Sheldon decided, after wisely making the choice to skip the "Star Wars" premiere to spend the night with her, that her present should be "[his] genitals." While the evening did begin with a bit of awkwardness, eventually the pair made it into the bedroom for what was ultimately a very sweet scene. 

Behind the scenes of the big moment, Bialik said a lot of care was taken to get the details of the scene right. For example, Bialik, who live-tweeted the episode from the account of her culture website, Grok Nation, says it was a game-time decision to have Sheldon and Amy in their birthday suits post-coitus. 

Bialik, who doubles as a neuroscientist, also penned an essay on Grok Nation explaining how much thought went into avoiding being exploitative with the couple's hot and heavy moment.

"We see that Amy’s hair is messed up in the reveal in the final scene. We see that she is tired and happy. The writers very delicately let me communicate the culmination of a lot of emotional and physical tension being released without it being gross or obnoxious," writes Bialik. "Sex is complicated, and so is intimacy."

Bialik added that she appreciated the show's respectful depiction of two "late-blooming" adults losing their virginity.

"In some ways, the loss of one’s virginity is sad. It is the end of a time in your life that won’t ever be the same. For some that happens very early, and for others it happens very late. That’s determined by circumstance and by cultural pressure and by peer pressure as well," writes Bialik. "I hope that Amy and Sheldon’s intimacy can be inspiring to those of you who are late bloomers, and encouraging for those of you who have yet to be intimate. And for those of you who are past the stage of thinking about the first time you were intimate, I hope this episode reminded you of the tenderness and the closeness and the possibility we all once had. If we are lucky, we get many chances to have that closeness even as grown-ups. And it can still be very sweet."

Watch Sheldon and Amy's sex scene in the clip from episode 11 below:

How will this big step affect Sheldon and Amy's relationship going forward? Fans will have to wait to find out. "The Big Bang Theory" Season 9 returns to CBS with new episodes on Jan. 7.