If you have an interest in the natural world and the building blocks of life, consider a biology project. When conducting a science fair project on biology, you should explain how something happens in the biological world. For example, you can explain the process of DNA forensics and how they help law enforcers identify and prosecute suspects. You can also try something a little more complicated like creating a detailed genealogy chart that shows the path of genetic mutations and diseases that pass from parent to child.
Psychology studies the mental inner workings of people. A psychology science fair project may be just up your alley if you have an interest in what makes people work the way they do. You can create a project that questions a person's average relationship between smell and memory, such as whether smell can help people recall situations more clearly. You may need several volunteers for a psychology project to ensure you get a healthy set of results that will help prove or disprove your hypothesis.
Humans and animals have a large impact on the state of the planet. Environmental science analyzes that impact and can help make a prediction about the future of the planet. Some examples of environmental science projects include observing the impact of livestock on a wild species or the effect of pollutants a specific life form. Observations may take a while to yield results in the environmental science field, so start recording data early.
Chemistry is your best option for a science project if you are hoping to create an explosion or chemical reaction. Chemistry studies the composition of materials and what reaction you get when you mix two or more materials together. Some chemistry projects include the study of how pesticides work to repel insects, but keep the crop edible for humans. You can also perform a project where you try to mix different chemicals to create something useful to society such as a wild animal repellent.