The nucleus is the "brain" of the cell. There are three parts of the nucleus that are important. The nuclear envelope protects the nucleus. Materials pass in and out of the nucleus through pores. Chromatin is thin strands that contain genetic material, the instructions for directing the cell's function. The nucleolus is where ribosomes are made. Ribosomes are the organelles were proteins are produced, which are very important chemicals in cells. This is found in both animal and plant cells.