This document from the Committee on Undergraduate Honors tells you everything you need to know if you're thinking of writing a thesis.
As you shape and narrow your topic, ensure that you can state it within this framework:
I am studying _____X____ because I want to find out _____Y____ so that my readers understand ____Z______.
X = your narrow topic
Y = your analytical question that likely starts with "how" or "why"
Z = a broad topic that your research connects to