Here's why:

* Nucleus: The nucleus is the control center of the cell. It contains the cell's genetic material (DNA) and directs the cell's activities.

* Organelles: Organelles are specialized structures within a cell that perform specific functions. Some examples of organelles found in animal cells include:

* Mitochondria: Powerhouse of the cell, responsible for energy production.

* Endoplasmic Reticulum (ER): Network of membranes involved in protein synthesis and lipid metabolism.

* Golgi Apparatus: Modifies, sorts, and packages proteins for transport.

* Lysosomes: Digest waste materials and cellular debris.

* Ribosomes: Sites of protein synthesis.

* Centrioles: Involved in cell division.

So, animal cells are complex structures with a nucleus and a variety of organelles that work together to maintain the cell's life.