In the 19th century, do-it-yourself x-ray kits became hugely popular as people x-rayed their own boots, hands, and plants (not to mention weirder stuff) to find out what the invisible world really looked like. Wired's Alexis Madrigal has a great article series with links to San Francisco's Museum of Modern Art's Brought To Light: Photography and the Invisible exhibit exploring these DIY pictures as part of the social consequences of x-rays and photography of the period.