Just like any other cells, animal cells are very small and cannot be seen by the naked eye. They are actually invisible to the human eye without using a microscope. The same microscope is what helped scientists discover the main components of the animal cell. A cross-section into the animal cell can indicate all of its components, just like in the picture below:

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Cell membrane: the thin protein and fat layer surrounding the cell;

Centrosome (also known as the microtubule organizing center): a small body near the nucleus where microtubules are made;

Cytoplasm: the place housing the organelles; it is very jelly-like;

Nucleus: the body controlling many of the cell’s functions; here is where the DNA is located;

Nucleolus: the organelle contained by the nucleus, where ribosomal RNA is produced;

Nuclear membrane: the membrane surrounding the nucleus;

Golgi body (or Golgi apparatus): the flattened, layered organelle looking like a sack that produces the membranes surrounding the lysosomes; 

Lysosomes (also knwon as cell vesicles) the round organelles containing digestive enzymes where the cell digestion occurs;

Mitochondria: the organelles converting the energy stored in glucose into ATP (adenosine triphosphate)

Ribosomes: the organelles composed of cytoplasmic granules that are rich in RNA and are the sites of protein synthesis;

Rough Endoplasmic Reticulum (or rough ER): the organelle transporting materials though the cell, producing proteins in sacks called cisternae;

Smooth Endoplasmic Reticulum (or smooth ER): the organelle transporting materials through the cell; it also contains enzymes and produces and digests both lipids and membrane proteins;

Vacuole: the organelle that fills with food being digested, as well as with waste material that is on its way out of the cell.