Hong Kong, April 29 -- Looking for some celebrity-approved haircut advice? These seven men's undercut styles are all you need.

When it comes to the affairs of men's grooming, celebrities have often led the way. Be it Hollywood or Bollywood, we've always looked up to the stars for inspiration. In their novice years, each guy has their moment where they see the hero on screen and go "I wish my hair looked that good". Thirty years ago, the old-school Pampadour had us saying that. Twenty years ago, it was the rock-star, slick back look and now, it's the undercut.

Even though the undercut has been around since the 1920s and was a go-to haircut for soldiers of war. However, in the early 2010s, this trend arguably picked up after Jon Hamm spor...