Do you know how to read a book with invisible contents? Croatian creative agency Bruketa & Zinić designed the annual report of food company Podravka in a very creative way.

The small Podravka booklet is printed in invisible, thermo-reactive ink and you need to bake it in order to read it.

However, you must be a precise cook and follow Podravka’s secret recipes: “to cover the small booklet in aluminium foil and bake it at 100 degrees Celsius for 25 minutes.”

If you are not precise enough or not a good cook, the book will burn if overcooked!