Histologic cross section of embryonic foot of mouse (Mus musculus) in 15.5 day of its development. There are still cells between fingers. (Full development of mouse lasts 27 days.)

There are two basic types of cells: Prokaryotes and and Eukaryotes. 

The prefix “pro-” means “before” and the suffix “-karyotic” comes from the Greek word “karyose” which means “kernel” (as in a kernel of grain), and refers to the nucleus of a cell; thus the term prokaryotic means before nuclei. Basically, any cell that lacks a membrane-bound nucleus is classified as a prokaryote. Usually, most prokaryotic cells are also bacteria and-unlike eukaryotic cells- are not dependent on oxygen and contain few determinable internal structures. 

On the other hand, the prefix “eu-” means “true” or “good” and again the suffix “-karyotic” refers to the nuclei of cells; thus the term eukaryotic means possessing a true nucleus. Eukaryotes (more formally known as Eukarya or Eukaryota) contain complex structures (organelles like mitochondria, chloroplasts, and the Golgi apparatus) enclosed within membranes and are usually much larger than Prokaryotes. Basically, all species of large complex organisms are eukaryotes. This includes animals, plants and fungi, although most species of eukaryote are protist microorganisms.
 

Apoptosis increasing from normal cells (top) to apoptotic ones (bottom).