What is the smallest cell organelle in a cell?

The smallest cell organelles are ribosomes. Ribosomes are spherical, dense organelles that range only 20-30 nm in diameter. They are the smallest organelle in a cell based on their surface area size. All ribosomes are composed of a large and small subunit and carry out similar functions for protein synthesis; ribosomes are composed of nucleic acids and proteins. The large subunit exists on top of the small subunit, with an RNA template between the two.