What role does the concept of human body composition play in the world of Fullmetal Alchemist?

In the world of Fullmetal Alchemist, the concept of human body composition plays a significant role in the story's exploration of alchemy and the consequences of tampering with the natural order. Characters in the series use alchemy to manipulate and transmute matter, including human bodies, leading to ethical dilemmas and moral questions about the value of human life and the consequences of playing "god" with the human form.