Happy 40th Birthday, Jennifer Lopez!

The actress celebrates a big one today, but she got the party started last night on set of her movie

Jennifer Lopez turns 40 years young today, but she kicked off the celebration last night.

The actress has been busy filming The Back-Up Plan in the Big Apple and took some time out to party with the crew and hubby Marc Anthony.

While she's definitely toned down her divalicious side since becoming a mom to twins Max and Emme, J.Lo.'s huge chocolate cake still paid tribute to...herself, what else?

It featured a big photo of herself and the message: "Jennifer...thanks for being our Plan A! You're the best. And...happy birthday!"

The birthday girl also got kisses from her hubby and toasted with champagne.

Despite turning the dreaded 4-0, a milestone that has most women pretending it doesn't exist, Jenny was beaming throughout the bash.

Do you miss her over-the-top J.Lo days or do you like the new softer, domesticated side of Jennifer?

Either way, happy birthday!