Ribosomes, also known as Palade granules, are organelles that are made up of both RNA and protein, whose function is to assist in protein synthesis. Essentially, ribosomes create a factory for protein synthesis in cells. Ribosomes are extremely small in size, ranging from 20 to 30 nm. They are granular shaped and are non-membranous organelles. The average mammalian cell has approximately 10 million ribosomes.  

Ribosomes were discovered in 1955 by George E. Palade, hence the alternative name  Palade granules. Each ribosome has a large subunit as well as a smaller subunit. Together, they create a single unit containing several ribosomal RNA molecules and dozens of proteins. Lastly, there are two types of ribosomes, prokaryotic and eukaryotic.