Whoa, baby. Justin Bieber is turning up the heat with his new ads for Calvin Klein. The 20-year-old pop star was named the new face of the brand's iconic #MyCalvins campaign on Jan. 6 and he's been flooding social media with sexy black-and-white teaser videos and photos.

In a new clip, uploaded on Jan. 7, Bieber is seen flexing his muscles and washboard abs, showing off his tattoos and, of course, giving fans a peek at his Calvin Klein boxer briefs.

"In #mycalvins," he captioned the video, including a link to the brand's website.

 In #mycalvins see more of my campaign at https://calvinklein.com/justin @calvinklein

A video posted by Justin Bieber (@justinbieber) on Jan 1, 2015 at 9:35pm PST

In other videos and photos, Bieber posed with model Lara Stone. So how exactly did Bieber become Calvin Klein's newest underwear model, a title previously held by Hollywood hunks such as Jamie Dornan, Mark Wahlberg and Mehcad Brooks?

"I've wanted to be involved with Calvin Klein for a while now," Bieber told US Weekly. "Earlier this year, I put up a picture on Instagram of me in their boxer briefs with the #mycalvins tag, and people went crazy for it and it got their attention."

He said the super-secret photoshoot took a few days to complete and was almost sidetracked when he got sick.

"It was actually two-and-a-half because I got sick during the second day," he said. "Behind the scenes, everything ran like clockwork - we'd come in, do glam, and get right to shooting."

Bieber also dished on how he got his rock-hard abs and told US that he worked out a few days a week with celebrity trainer Patrick Nilsson.

"I work out with my trainer, Patrick Nilsson, five days a week for about 45 minutes each," Bieber said. "We do three days splits: back and triceps one day, chest and biceps on day two, shoulder and legs on day three, and abs every other day."

"I'm not on a special diet," he added. "But I do try to watch what I eat. I do eat unhealthily sometimes - I am a 20-year-old guy!"