Nothing is permanent in this world. A ballpoint pen with erasable ink and paper that self-erases proves this.

Pen maker Pilot produces a special eraser that rubs off the ink of its Frixion variety ballpoint pens.

The product inspired Japanese Professor Hiromi Uchimura, 64, of Ehime University, to develop a unique paper that can erase what is written on it.

The erasable paper has a built-in timer to allow erasures after a certain time set by its user, after which the ink becomes indelible. A patent for the paper was registered in February, Asahi reports.

Uchimura explained to Asahi that a coating material called cellulose nanofiber makes the paper erasable.

Meanwhile, designer and inventor Joe Doucet of Katonah, New York, has come up with a new solution to keeping homes warm in the winter and cool in the summer using two colors.

Inspired by mood rings, which feature man-made “stones” that change appearance according to the wearer’s finger temperature, Doucet developed a kind of thermochromic pigment containing liquid crystals that causes color to change, CNN reports.

Doucet then added a protective additive to make the paint withstand degradation from the sun’s heat. The patented house paint can adjust interior temperatures depending on the season.

Originally dark gray, like the black houses in chilly Scandinavia, to make the exterior absorb sunlight during winter, Doucet’s paint turns lighter as temperatures rise going into the summer season.

Light colored paints reflect light and heat, lowering interior temperatures.

Doucet said his patented changing color paint -- black to white -- is ideal for homes in the world’s temperate zones, including large parts of North America, Europe and Asia, according to CNN.