Ribosomes, my favorite part of cells, are also one of the most complicated parts of cells. They are protein structures that synthesize proteins from amino acids. The are found both free-floating in the cytoplasm of cells and also attached to the Rough Endoplasmic Reticulum. Wherever they're found, their purpose is the same: make proteins. They take "instructions," found in mRNA, and translate them into the amino acid sequence of a protein.
On the left is an image of a ribosome. As you can see, it is nothing more than a coiled mass of protein and nucleic acid that functions to create proteins.
They are made up of two subunits, as demonstrated by the two different colors in the picture. They are assembled in the nucleolus, which is a small structure located with in the nucleus.