Haring first received public attention with his graffiti art in subways where he created white chalk drawings on a black, unused advertisement backboard in the stations. He considered the subways to be his "laboratory", a place where he could experiment and create his artwork and saw the black advertisement paper as a free space and "the perfect place to draw". The Radiant Baby, a crawling infant with emitting rays of light, became his most recognized symbol. He used it as his tag to sign his work while a subway artist. Symbols and images (such as barking dogs, flying saucers, and large hearts) became common in his work and iconography. As a result, Haring's works spread quickly and he became exceedingly more recognizable.