A letter from the Revolutionary War with lines written in invisible ink. Credit: Wikimedia Commons Last year, the US Central Intelligence Agency released documents detailing recipes for invisible ink ...

Add Yahoo as a preferred source to see more of our stories on Google. Need some gifts for your kids, grandkids, nieces and nephews? More specifically, gifts they won't toss aside as soon as they open ...

Coded messages in invisible ink sound like something only found in espionage books, but in real life, they can have important security purposes. Yet, they can be cracked if their encryption is ...

Add Yahoo as a preferred source to see more of our stories on Google. William Abel, a mail censor at Iowa's State Prison, Fort Madison, using a hot iron to bring out a secret message written in lemon ...

Once iOS 10 officially launches on Sept. 13, we’ll have loads of new features to play with — including the new Bubble Effects in Messages, Apple’s text messaging app. I do have to say, though, that ...

A novel invisible ink tattoo technique may improve long-term quality of life and emotional well-being for people with cancer who undergo radiation therapy, according to study results. Radiation setup ...