Final answer:
The lowest level of organization in the human body is the chemical level, including subatomic particles, atoms, and molecules, which form the foundation for all higher levels of structure.
Step-by-step explanation:
The lowest level of organization in the human body is the chemical level, which includes subatomic particles, atoms, and molecules. These are the most basic building blocks from which all other structures are built. For example, atoms combine to form molecules, and these molecules can then combine to form more complex structures like organelles and cells, the latter of which is often cited as the basic unit of life.
Progressing from these small beginnings, cells organize into tissues, tissues into organs, organs into organ systems, and finally, organ systems integrate to form a complete organism, which represents the highest level of organization.