I first became interested in fundamental physics in secondary school, when a teacher described the basic idea behind a grand unified theory. 

Currently, physicists are able to describe the behaviour of the known particles using just four forces. These are called the strong force, the weak force, the electromagnetic force, and the gravitational force. A grand unified theory tries to combine the first three forces together into a single force. (A theory which attempts to also include gravity is known as a theory of everything.)

My current research focuses on how certain special number systems in mathematics might ultimately underlie the behaviour of elementary particles. This can be thought of as a form of unification, but not in the traditional sense.

Mathematical physics is a beautiful subject, which gets better and better the further you go. It is elegant, much unlike the sorts of things that you will learn in first- and second-year physics. If you are interested in physics and are mathematically inclined, then know that the abstract, beautiful material starts appearing more around your third year.

This area of research has not progressed in terms of gender diversity, as most other fields have. This means that if you would like to pursue this line of study, then you will need to develop a very strong sense of self. Sometimes even your own friends and teachers will unintentionally fix ridiculous stereotypes to you. Just do your work, and prove them wrong.