How are sand dunes formed and how tall can they get in real life?

Sand dunes are formed through the action of wind, which moves sand particles from one location to another, causing them to accumulate and shape into mounds or ridges. The size of sand dunes can vary greatly, with some reaching heights of over 500 feet (about 150 meters) in places like the Badain Jaran Desert in China. Factors such as wind direction, sand supply, and vegetation can influence their height and shape.