Tea bags were invented accidentally - the inventor, Thomas Sullivan, decided that it was cheaper to send small samples to potential customers in silk bags
Today, it is almost odd if you don't use a tea bag to make tea. Yes, there are those fancy places that infuse the tea right there and have no need for a tea bag.
Most of the time though, you're grabbing a tea bag, dunking it in hot water and getting to work. If it hadn't been for Thomas Sullivan though, tea bags may never have been invented.
Sullivan actually invented them by mistake. In 1908, he was a tea merchant in New York city and looking for an easy way to send tea samples to his customers.
He found that it was more convenient to send the samples in small silken bags rather than boxes. Some of his customers assumed these bags should be used like an infuser and put them right in their cup.
These customers told Sullivan that the silk was too fine so he developed bags made out of a gauze material.
Tea bags started being produced commercially in the 1920s, and they grew in popularity. Two sizes were told - a large one for the tea pot and small one for the tea cup. They also already had the string that made it easy to remove the bag from the tea.