What are the main methods of studying nature?

There are 2 main methods by which we study nature.
1. Observation. This is the easiest method. We do not need complicated devices or formulas for it. You just need to show observation and patience. The observation method involves fixing all the changes that occur in nature. For example, we observe how a leaf appears from a bud on a tree, how it grows, then turns yellow, becomes dull and falls to the ground.
2. Experiment. If observation is a passive method, then the experiment involves some kind of human intervention. For example, we do not just observe the leaves, but expose them to radioactive radiation.