László Bíró, a Hungarian journalist, invented the ballpoint pen after noticing that newspaper ink dried quickly and didn't smudge. He realized that a thicker ink was needed, but it wouldn't flow through a regular fountain pen. He developed a design with a tiny ball bearing in a socket that could rotate and pick up ink from a cartridge, transferring it to paper. The British Royal Air Force were the first major customers, as ballpoint pens didn't leak at high altitudes like fountain pens did. After the war, the 'Biro' (as it is still called in many countries) became the world's most popular writing instrument. It made writing cleaner, more reliable, and more affordable, completely replacing the need for inkwells and blotting paper in daily life.