FIRST PIC: Meet Jim Carrey's Brand-New Grandson!

Barely a day old, Jim Carrey's first grandson Jackson Riley Santana is ready for his closeup!

Carrey, 47, posted his very first photo of Jackson via Twitter. As the actor's rep confirmed to UsMagazine.com, the new addition was born at 12:28 a.m. on Friday in Los Angeles.

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"Jackson Riley Santana, My Grandson, Born today! This is what 7lbs.11oz. of Calfornia dynomite [sic] looks like! %^>," the star wrote early Saturday.

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Little Jackson is the first child for Carrey's 22-year-old musician daughter Jane and her husband Alex Santana (a.k.a. "Nitro" from the band Blood Money). The couple married in November of last year.

"Jane is going to be a great mom," Carrey told Us last July following the announcement of his daughter's pregnancy.

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His girlfriend of five years Jenny McCarthy, 37, recently joked to Us that she will make an "awesome grandma...the world's best!