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 ...

A team of researchers were trying to develop an eco-friendly alternative to petroleum-based ink by using algae when members discovered they had accidentally created invisible ink that changes over ...

Some of the best inventions actually started out as accidents, and such is the case with the world’s first “Chia Pet” pen. Its creators were trying to create an eco-friendly alternative to printer ink ...