Big changes are in store for The Big Bang Theory. Recently, executive producer Steven Molaro spoke with EW about season 10 of the CBS sitcom.

Earlier, we reported the new season will include guest appearances from Katey Sagal, Keith Carradine, Jack McBrayer, and Dean Norris among others. The regular cast includes Kaley Cuoco, Jim Parsons, Johnny Galecki, Kunal Nayyar, Simon Helberg, and Mayim Bialik.

In the interview, Molaro said the season premiere will introduce Penny’s family:

She’s close with her dad. As we know, her brother Randall has been a bit of trouble over the years, selling drugs and being in and out of jail, and that’s put a lot of stress on her mom, so I think the stress between her mother and her brother can make things a little tense. You will pick up on the tensions between her mother and her brother very quickly. You get a glimpse of Penny and her dad being caught in the middle of that.”

And as for Sheldon and Amy, he said fans can expect some “experiments”:

I don’t want to give away too much, but there are some big experiments in store for them and their relationship. … But I’m stressing the word experiment and it’s something that would they even consider it? Well, usually it’s a good way to trick Sheldon into doing things is by framing it in terms of science.”

Molaro later added that season 10 will continue to see the characters grow:

The characters continue to grow, their relationships mature and we’ll just see where it takes everybody. As you know, their growth is organic and we don’t plot out an entire year, so it keeps it exciting for us, because we never know exactly what’s going to happen until it does and it can even catch us off guard in the writer’s room, which I love.”

Season 10 of The Big Bang Theory premieres on tonight, September 19th, at 8 p.m. ET/PT. 

What do you think? Do you watch The Big Bang Theory? What do you hope happens in the new season?