It started with hair. Donning a pair of rubber gloves, Heather Dewey-Hagborg collected hairs from a public bathroom at Penn Station and placed them in plastic baggies for safe keeping. Then, her search expanded to include other types of forensic evidence. As the artist traverses her usual routes through New York City from her home in Brooklyn, down sidewalks onto city buses and subway cars—even into art museums—she gathers fingernails, cigarette butts and wads of discarded chewing gum.
For the rest of the story: http://myscienceacademy.org/2013/05/05/creepy-or-cool-portraits-derived-from-the-dna-in-hair-and-gum-found-in-public-places/