[Junior]

Once again, the word "fact" never enters into it. Researchers "observe" the human body (or whatever they are studying) and make "theories" to explain those observations.

[CyberCowboy777]

It does not end with theories.

scientific method - The principles and empirical processes of discovery and demonstration considered characteristic of or necessary for scientific investigation, generally involving the observation of phenomena, the formulation of a hypothesis concerning the phenomena, experimentation to demonstrate the truth or falseness of the hypothesis, and a conclusion that validates or modifies the hypothesis.