This is a good question. Essentially the lava lamp can be explained by using the physical laws of fluid dynamics. It uses the fact that substances heavier than water sink in water but lighter ones go to the top. Here a lamp heats a glass container filled with water and a mix of oil and wax – which you see floating around in the lamp. The reason why the you see the nice floating around is because the density of the oil/wax mixture, and also the ability to sink and raise, depends on temperature which is varied by the lamp, and the oil/wax mixture can raise and sink in a very nice way depending on how the exact temperature around the mixture is.