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 ...

Hillhouse students at work writing invisible ink messages … … after their teacher, Kate Goodwin, applies heat to reveal invisible messages in class about the ...

For a long time, seeing those words pop up onscreen was the best indicator of good gossip to come. Close seconds included “OK, so…” for the more demure among us, or a simple teacup emoji for the ...

Which invisible ink pens are best? Spies and conspirators have used invisible inks for millennia to send messages. In the modern age, invisible ink pens are an excellent way for grown-ups to ...

ALBUQUERQUE, N.M. (WHAT THE TECH?) — Like cyber criminals with AI, parents might be interested to know that people have been using invisible commands for years on apps we all use. When some of us were ...

My finger hovers over an iMessage obscured by a haze of dancing white dots. Before I tap to dissolve the sparkling pixels and reveal the contents of the message, I know it's going to be juicy, or at ...

It is a classic rite of passage for nerdy kids to write secret messages using lemon juice. If you somehow missed that, you can’t see the writing until you heat the paper up with, say, an old-fashioned ...

Have mini detectives, secret agents, or superheroes at home? Keep your creative kids entertained for hours with this fun DIY invisible ink recipe that uses ingredients straight from the kitchen! There ...

Jake Peterson is Lifehacker’s Tech Editor, and has been covering tech news and how-tos for nearly a decade. His team covers all things technology, including AI, smartphones, computers, game consoles, ...

A Hillhouse student’s eyes widened as he applied grape juice and heat to what appeared to be a blank piece of paper — but instead held a secret message in invisible ink, written as part of a course ...

SHREVEPORT, La. — When we were kids, “invisible ink” meant lemon juice on notebook paper — write the message, and to see it someone would have to hold it up to the light for the words to appear.