Nucleus

All eukaryote cells have a nucleus (except for red blood cells). The Nucleus to the Cell is like the Brain to the Human. It controls all the functions within the cell, "makes the decisions." The Nucleus makes the Ribosomes, which themselves make the DNA for the cell.
The Nucleus itself has many parts. Its made up of Chromosomes and Chromatin, the Nucleolus, the Nuclear Envelope and the Nuclear Pores. Each serving a special function to the over all Nucleus. The Chromosomes the DNA needed for the cell, body and overall organism to live. The Nucleolus is the organelle that manufactures Ribosomes. The Nuclear Envelope is the membrane of the Nucleus that protects the Nucleus from other things. Finally the Nuclear Pores. These "pores" are found on the Nuclear Envelope and they are the ones that let molecules and ribosomes in and out of the Nucleus itself.