‘National Geographic Taboo,’ since it’s creation in 2002, has always taken a look at society’s weirder trends. But never has it received more attention than with it’s most recent subject, “Bagel Heads.”

In last night’s episode, the show featured an ongoing trend in Japan with extreme body modification. The customer would have saline (sterile salt water) injected into the forehead to create swelling. Then, the person injecting the solution would press gently in the middle of the swelling to create the “bagel” affect.

The trend started several years back with underground body modification journalist Ryoichi “Keroppy” Maeda, according to Vice.

Maeda explains that the process of injecting saline usually takes around two hours, but it will dissipate after only one night.

While intensely bizarre, Maeda, who has been researching the subject for two decades, revealed that the trend isn’t one of the more extreme in Japan. He notes, “ear pointing, naval removal,” and “amputation” as some of the more extreme trends.

He explains the reasons why it’s happening more clearly; “Well, you know, people who like extreme body modification want to find their own way of doing things, and they’re always looking for new ways to do that. The more progressive the scene gets, the more these people have to experiment and go their own way.”