I think the greatest invention in human history is airplane. In the ancient world, people had made a lot of effort to design such a device, but it was not until the early 20th century that people were finally capable of flying with the work of the Wright Brothers. Now we can fly at speeds of up to 800 kilometers per hour, it greatly shortens the time we need to spend on travelling between two cities or two countries. We can also have a trip to our dream city much easier.