Here's why:

* Cells are the basic unit of life.

* Organelles are specialized structures within cells that carry out specific functions. Ribosomes are responsible for protein synthesis, a crucial function for all cells.

* Tissues are groups of similar cells that work together to perform a specific function.

* Organs are composed of different tissues that work together for a common purpose.

* Organ Systems are groups of organs that work together to carry out major bodily functions.

* Organism is a complete living being composed of multiple organ systems.

Therefore, ribosomes, as specialized structures within cells, fit into the organelle level of organization.