Gold nanoparticles can make the pink "get ready to be a parent" mark on home pregnancy tests much easier to read. When a woman gets pregnant, her body immediately starts making the hormone human chorionic gonadotropin (hCG). As the potential mother urinates into a sample-collection area and the pee migrates to a test strip, some of the antibody-coated gold nanoparticles on the strip latch onto the hCG, migrate up the paper, and collect at an indicator line. If the chemical is not present in her urine, all of the pink nanoparticles will drift up the strip, past the pregnancy-indicator line to a second marker.