When I was a kid, my parents had a collection of historic old, yellowed newspapers. For example, I distinctly remember an oldWashington Post newspaper sitting on a bookshelf from July 21, 1969 with the headline "The Eagle Has Landed – Two Men Walk on the Moon." Or a fading, brownish-yellow one from August 8, 1974 with the big headline, "Nixon Resigns." These newspapers are fascinating artifacts documenting history, from remarkable moments to the relatively mundane. Unfortunately, they were also hard to read due to the yellowed, brown color and fading print. So why do old newspapers – and books – turn yellow? And is there any way to prevent this from happening?