Graffiti as an art form began in Washington Heights. As bombing became competitive, the foundations of an inter-borough competition were established with important hubs, such as the writer's bench, elevated trains, train yards and lay-ups located in the South Bronx. In the early 1970's South Bronx writer Phase2 invented bubble letters and created the first throwies and Wild Style lettering. Writers like BG183, BIO, Brim, Mack and Nicer emerge from this tradition, and form crews like Tats Cru during the 1980's in the South Bronx. Closely tied to the birth of hip-hop in the Bronx, Tats Cru worked with DJ Cool Herc, Grandmaster Flash, and others. Later they collaborated with rappers such as Blg Pun, Fat Joe and KRS One. As the MTA cracked down on train graffiti, these writers began painting walls. Tats Cru continues to paint walls, using the art form and partnership to preserve the community, culture and history of the South Bronx today. Tats Cru maintains a studio in Hunts Point, and with other Bronx based artists, such as CRASH and DAZE are establishing an arts district.