(Cover) - EN Showbiz - Rebecca Romijn says having twins is like a "crazy social experiment", revealing her daughters are growing up to be very different.

The actress and her husband Jerry O'Connell have two-year-old twins Charlie and Dolly and she has noticed they are already developing individual personalities. While Charlie appears to be more feminine and interested in fashion, Dolly is showing a passion for risk taking and is a real tomboy.

"It's just like a crazy social experiment where you have these two people who were born on the same day, who have been raised in identical upbringings in the same bedroom and they could not be more different as people," the actress explained during an interview with American talk show host Rachael Ray. "People are just born how they are born and there's nothing you can do to change that."

Rebecca revealed her daughter's differences really became apparent when they sat down to watch the British royal wedding last month. Although Charlie was transfixed to see Prince William marry Catherine Middleton in a lavish ceremony, Dolly was more interested in jumping off furniture.

"Their reactions to it could not have been more polar opposite. Charlie is going, Princess, princess, princess,' with starry eyes and Dolly was running out of the room going, No, no, no!'" Rebecca laughed. "Charlie, since she was a baby, if I get dressed up for something, she's the one who looks me up head to toe, checks out my shoes, takes it all in. Dolly's never noticed.

"[She's like,] Where is a giant piece of furniture I can stand on top of and almost die?'

"I feel like we're getting through the death watch period where they might almost die, but hopefully we're going to start communicating and explain why you can't stand on that really tall piece of furniture."

Rebecca, 38, explained the twins are growing up so quickly that she is sometimes afraid to take them out on her own. They are beginning to run very fast and Rebecca is terrified they could hurt themselves if she doesn't get to them in time.

"They're at this age where they run off in opposite directions from one another, so I'm still not really brave enough to take them out alone by myself because you can't run in two directions," she added. "So if you're in the middle of the parking lot and they both just drop dead weight Jerry's big enough, he's brave enough, to scoop down and pick them both up, but they're getting to be big people!" (C) Cover Media