As London-based photographer Brian David Stevens says, "we see graffiti all the time." The difference is, he wanted to meet some of the people who created it.
So that's what he did - the results being a striking collection of photographs which reveal the people behind the tags.
Stevens says the distinction between street art and graffiti is important. "There's a big difference between the them. Although the two scenes do overlap, I found graffiti to be a lot rawer and in some way more pure."
It also tends to be a lot more anonymous than street art, and part of the challenge of Steven's project was cracking into the subculture's social groups. "Trust is important", he told HuffPost UK.
"I let the writers see what I was going, gave them prints. It became a collaboration."
"I met some really nice people, really creative guys and girls. But obviously people will be suspicious of your motives as writers are going to prison for illegal painting, with pretty draconian sentencing."
"After hanging around long enough they got understood what I was after. I took the pictures on a semi-legal site and made sure that the subjects weren't really identified to get round any legal problems. You have to put the hours in."
These images show the human side of graffiti, shots of 'black book' sketchbooks demonstrating the artistry that can motivate what many would deem vandalism.
"You learn how deep people are in the scene," Stevens says, "They live and breathe graff."