There are two main types of cells: prokaryotic and eukaryotic. Prokaryotic cells, like the bacterium pictured here, are simple cells. They don’t have a lot of internal parts, just cytoplasm, and DNA floating in the middle—with no nucleus. In contrast, eukaryotic cells are complex, with lots of parts and a nucleus that holds and protects the DNA. (Blue Ring Media/ Shutterstock) Read More