1. Prokaryotic ribosomes: These ribosomes are found in prokaryotic organisms, such as bacteria and archaea. They are composed of a small subunit and a large subunit, which come together to form a complete ribosome when needed. Prokaryotic ribosomes are typically 70S in size, where "S" stands for Svedberg units, a measure of sedimentation rate.

2. Eukaryotic ribosomes: These ribosomes are found in eukaryotic organisms, which include animals, plants, fungi, and protists. They are more complex and larger in size compared to prokaryotic ribosomes. Eukaryotic ribosomes consist of a small subunit, a large subunit, and a number of additional factors that assist in protein synthesis. They are typically 80S in size.

Within these two main types, there can be further classifications based on the specific organism or organelle where the ribosomes are located. For example, in eukaryotic cells, there are ribosomes present in the cytoplasm (free ribosomes) and ribosomes attached to the endoplasmic reticulum (rough endoplasmic reticulum). Each of these types of ribosomes may have specialized functions related to protein synthesis.