Geochemistry
Geochemistry studies the chemical composition of the Earth and other planets as well as the Chemical processes taking place there. I was always fascinated by the fact that we are made up of minuscule entities: atoms, protons, quarks etc. and that their balance or interaction defines everything that is or could be. The composition of rocks, water, and soils; the cycles of matter and energy.
"I died a mineral, and became a plant. I died a plant and rose an animal. I died an animal and I was man. Why should I fear? When was I less by dying?" - Jalal ad-Din Rumi
An understanding of earth and life is not complete without understanding the chemical processes and balances behind them; these do not only define everything, they are the essence of everything.