They were put together when their agency decided to create the perfect boy band with a new more masculine concept. Only two of them, Jun K and Jay Park (Yes, the now famous Jay Park), had previous experience. The remaining five were recruited; four through a nationwide talent search program, and the remaining member from the shores of California no less. So that tells you that they were originally seven instead of six. For the first several years they lived in a dormitory-like situation and trained intensively in voice, dance, weight lifting (they were known as the "beastly" idols), and even acrobatics. They became a very close-knit group and recently held their 15th anniversary concert in Korea and Japan. Their live performances are fire.
They have known each other since about 2006 as trainees at JYP and debuted in 2008. This song came out in 2015, but their chemistry was always exceptional. The group members always say that if you really want to see what they can, do you need to watch a concert. I agree 100%, and I have only attended concerts online. They love being on stage together. Their catalogue is extensive and amazing and they are absolutely hilarious. Three hours passes in a blink of an eye, they don't want to leave the stage, and the audience doesn't want them to go. It is amazing.