All right.

Leonard is attempting to learn why subatomic particles move the way they do.

Really?

That's it?

Well, that doesn't sound so complicated.

It's not.

That's why Leonard does it.

That is a beloved and brutally honest Sheldon Cooper from the CBS comedy, The Big Bang Theory.

Actor Jim Parsons has brought Sheldon to life for the past 10 years on this hit show.

And now he's also behind the camera as executive producer and narrator of a new show.

It's called Young Sheldon.

The series introduces us to the eccentric scientist as a child.

Ian Armitage stars as a boy genius in the prequel to The Big Bang Theory.

In this preview of the premiere episode, the nine-year-old Sheldon goes on his first day of high school.

Oh, dear.

Yeah.

That boy has an exposed tattoo.

He does.

I wonder if he knows that's in violation of the dress code.

Speaking of which, how about we lose the bow tie?

Why?

Look around, honey.

None of the other kids are wearing one.

Well, perhaps I'll start a fight.

No, you won't.

Please trust mommy.

All right, tell you what.

You take it off, and this weekend, I'll take you to Radio Shack.

Hm?

Every kid wants to go to Radio Shack.

We are pleased to welcome Jim Parsons and Ian Armitage to Studio 57.

What were you going to say, Ian?

So I was going to say, you earlier asked me to think of three words that were, like, really funny.

Yeah, three lines, three lines. And actually, I have four.

OK, go ahead.

Thank goodness.

Go ahead, give me three lines.

Go ahead.

First of all, that girl's blouse is diaphanous.

Like that?

Which means I can see her brassiere.

OK.

Second of all, we have, mom, when should I be expecting my testicles, your favorite one.

Yes, that is my favorite line in the pilot.

Third, we also have, perhaps I'll start a fad.

Yeah, we saw that one.

And fourth, let me think.

Well, we'll go to Jim, and you think of the last one.

But Jim, this was your idea.

You went to Les Moonves and said, wouldn't it be fun to show Sheldon before?

What were you thinking?

Why did you think we're onto something here?

Because you really are.

The first thing we were trying to think of, it was me and my production company.

Anything related to that we could take a show out about.

And we were going with my nephew.

That was the first thing.

He's a 10-year-old.

He's 11 now in Texas.

He's very smart.

And as we started talking about it, it was like, well, this is describing a young Sheldon, or it could be.

So I checked in with Chuck, first of all, because I thought, if he has any interest in this, I should talk to him about it.

But I didn't think he would.

I really thought, I was like, they would have thought of this before.

They've been building the material for it for a decade.

I mean, we've had anecdote after anecdote about young Sheldon that Big Sheldon has talked about.

But they jumped at it.

And what they've done with it is really miraculous, in my opinion.

It is its own show.

It's its own memory play.

It's an origin story.

What were you going to say?

I love how you don't refer to yourself as Old Sheldon.

What I call myself.

You called yourself Big Sheldon.

Big Sheldon.

Oh, yeah. So it only makes sense for there to be an old Sheldon.

But I love how you don't.

That's the nicest thing I'll say about myself today, probably.

Just big, not old.

I also thought of the fourth one.

OK.

Go ahead.

Think, monkey, think.

Think, monkey, think.

Ian, what did you, when you've starred in Big Little Lies, and so a lot of people know of you, but what did you think when you got this character?

Oh my goodness.

I was so happy and excited that it was, like, I was just, it came sort of as a total shock, because I thought, oh, yeah, I get to do another audition.

I was at my grandma's over Christmas.

I just barely even memorized it.

And I was just like, my mom filming it was probably the best thing about it.

And then I got a call back, so I was like, oh, well, that's pretty good.

So I went in, I did it, and I met Mr. Jim.

Well, you nailed it.

So who's responsible for you being an actor?

You or your mom?

Well, you see, it doesn't exactly run in the family, because my mom's not an actress, but my dad is an actor.

And you just saw him this weekend.

Yeah, I did.

I saw him in Hamilton, but the only difference is he's a theater actor, and I act in TV shows and stuff.

I did actually do a thing.

It was called Millions.

It was, oh, I'm blanking, a workshop.

A workshop.

But you know, this is the thing that's so cool about this role, Jim, is that for his character, for Ian's character, you're not just putting Sheldon's words in his mouth.

No.

It's not like you're trying to do adult words for this little boy.

No, one of the things we've been talking about a lot is that it really is its own character, in the same way that, because what you're seeing is Sheldon, how he became what we see in the adult show.

And so this is kind of its own creature that he's portraying here.

And there are overlaps, but there's also, like, we watch him discover things like comic books.

We watch him discover things like his clothes are going to change style as he goes through this.

And I don't know.

It's like all the things that you associate with Sheldon now, you see how they got there through him.

Yeah.

And what's it like, Jim?

Because we are used to seeing you in front of the camera to now have this additional role as a producer.

I'm very mediocre at it. That's what they say about you, Jim.

That's not true.

Well, that isn't true, is it?

Not true.

There's nothing about you mediocre.

It's very strange.

And it's taken a lot to get used to even talking to another actor, in this case, Ian, like.

Giving direction?

Sort of.

I mean, you know, I've never been someone who's comfortable giving other actor direction.

And, you know, I don't know what makes any other actor tick necessarily.

And I don't want to break it, you know, so, or him.

But he's, Ian's very smart.

I'm not that fragile.

No, you're not, actually.

I mean, I'm fragile, but I'm not that fragile.

You're flexible and resilient.

Pliable, yeah. Good, Ian.

But he, Ian's just so easy to talk to.

OK, so one of the other interesting things, this actually takes place in 1989.

And you were not alive in 1989.

I was not alive.

Right, we were all alive.

So what were some of the funny things you learned about the 80s from doing this show?

First of all, the clothing sort of took me by surprise.

Because you have a lot of things that would be considered totally outdated and really weird today.

And stuff like that.

No cell phones?

Yeah, no cell phones.

No cell phones.

You had those like huge old, huge things, whatever they are.

And Big Bang's coming back too.

It ended with you proposing.

So we'll find out, did she say yes?

We get an answer tonight.

And in real life, you've gotten married after many years.

I did, yes I did.

You and Todd, congratulations.

What took you so long to make honest people out of each other, honest men?

You and Todd.

You were dating a long time, Tim.

Almost 15 years now.

I think it was just when we first got together and it was a real thing between us and we knew it was probably long lasting.

Marriage wasn't a possibility.

And we went on so long that even once it was, it wasn't, we were like, well, we're happy though.

But then we said, what the hell?

Let's have a party.

What the hell?

Congratulations.

Thank you. Such a great show. If you call happily ever after, what the hell, then.

Jim Parsons and Ian Armitage.

Young Sheldon, you can see this season's 11th premiere of the Big Bang Theory tonight.

Children pick up everything, Jim, at eight, seven central.

That's followed by the series premiere of Young Sheldon at 8.30, 7.30 central.

Right here on...

CBS.

Good for you.

I had that.

All right, you can hear more of our CBS This Morning on our podcasts on iTunes.