neighborhood. >> can we talk to you about your pillow? >> to collect pillows for microscopic testing. >> can we have this? >> reporter: to see just how filthy they can get. we got one. >> my son has pillows that i don't want to know what's in them. >> reporter: in all, eight pillows. some looking and smelling worse than others. >> this one's falling apart. >> reporter: teaming up with university of arizona microbiologist charles gerba to test the pillows for bacteria and mold. and the results stunned even him. >> yeah, surprised in some of them how it varied. >> reporter: the third dirtiest pillow belongs to this guy, dominik. the bacteria count is about as bad as the average unwashed countertop. we shared the news with him and his mom. >> does this surprise you that even in a house this clean the pillows still get dirty? >> yes.