Nucleus

The Nucleus encompasses the cell's hereditary information and controls the cell's growth which include metabolism, protein synthesis, and reproduction (cell division).

It is the most prominent organelle in a cell.

The Nucleus is surrounded by a double membrane called the nuclear envelope, this envelope helps maintain the the shape of the nucleus and aids in managing the flow of molecules into and out of the nucleus via nuclear pores.  

 

Nucleolus

The nucleolus is a round body located inside the nucleus of a eukaryotic cell. It is not surrounded by a membrane but sits in the nucleus. The nucleolus makes ribosomal subunits from proteins and ribosomal RNA, also known as rRNA. It then sends the subunits out to the rest of the cell where they combine into complete ribosomes. Ribosomes make proteins; therefore, the nucleolus plays a vital role in making proteins in the cell.