Today, 3M makes over 300 different Post-it products, ranging from page markers all the way up to easel pads. Orr said the original 3x3 yellow note pads are still one of the highest sellers.

3M then took it further and started manufacturing Post It Notes in 1977 ... 3M has sold 2 trillion sticky note pads. They turned out to be one the most significant inventions of the 20th century ...