Here's why:

* Functional Structure: Organelles are specialized structures within cells that perform specific functions.

* Confines of a Cell: Organelles exist within the cytoplasm of a cell.

* Literally Small Organ: While not organs in the traditional sense, organelles are often referred to as the "organs" of the cell due to their specialized functions.

* Membrane-Based Structure: Many organelles, like mitochondria, chloroplasts, and the endoplasmic reticulum, are enclosed by membranes.

Examples of Organelles:

* Nucleus: Contains the cell's genetic material (DNA).

* Mitochondria: Responsible for cellular respiration and energy production.

* Golgi Apparatus: Processes and packages proteins.

* Endoplasmic Reticulum: Plays a role in protein synthesis and lipid metabolism.

* Lysosomes: Digest cellular waste and foreign materials.

Let me know if you have any more questions about cell structures!