It's all about the ink! Most erasable pens use a special kind of ink called thermo-sensitive ink. When you jot something down, the ink appears just like normal. But when you need to make changes, use the eraser on the pen (or a separate one), and the ink becomes invisible – like magic! The technicals: Thermo-sensitive ink contains special compounds that respond to temperature changes. When you erase your ink, the friction causes heat, and the ink undergoes a chemical reaction, changing to a colourless state. Fun Fact: the ink is not removed in this process, it is still on the paper - it is just invisible.