There are basically 5 types of science fair projects. First you need to ask yourself what you want to show with your project. There are projects to conduct an experiment where you test something to prove your hypothesis. Another type is a demonstration to show how something works. A third project can be a research project where you can collect data about something. One of the most popular types of projects is to make a model of something like a volcano to show how they work. A more intersesting project is to build a collection of something like rocks or butterflies. The best thing is to decide what you want to learn more about and choose.