.Engine Principle: The shape memory alloy boasts memory after heat treatment, which changes the shape through the temperature difference of the phase transformation point. The nickel-titanium wire is straightened. When the temperature is high, it will be straightened, on the contrary, the temperature is soft. A constant cycle between the two temperatures will make the engine work. .Mechanical Knowledge: Observe the whole working process of the engine to brief on its structure&principle and feel the magic process of energy transformation. Meanwhile, the engine is inducive to hands-on ability, learning interest and creativity. .How to Use: 1. Install the flywheels on both sides of the crank mechanism in the engine package. 2. Put the nickel-titanium wire on the two flywheels. 3. Prepare a cup of 70°C hot water, put the small end of the engine in warm water and turn the flywheel to give its initial speed, so that the engine begins running. And it will decelerate to stop when it leaves the water. .Notes: Pay attention to being scalded by hot water when playing. The diameter of nickel-titanium alloy wire is 0.49mm, which is dangerous. Children should use it under the guidance and help of adults. .Superb Gift: The astounding mechanical craft, as a talking point that is packed with an elegant graphic carton for beauty&high value, is perfect for children and technology lovers being a creative and impressive gift for friends, families, teachers and students on birthdays and Christmas. Recommended for 8+.