On today’s broadcast of NPR’s “Science Friday”, Professor Kristie Macrakis of the Georgia Institute of Technology discussed her new book Prisoners, Lovers & Spies: The Story of Invisible Ink from Herodotus to Al-Qaeda. The interview led off with a discussion of the use of lemon juice as invisible ink, which dates back to classical antiquity!

For more on the broadcast and Prof. Macrakis’ book, visit the “Science Friday” page.