This chapter focuses on eukaryotic cell structure and function. Although prokaryotic organisms are immensely important in microbiology, eukaryotic microorganisms - such as fungi, algae, and protozoa - are also prominent members of many ecosystems, and some have medical significance as etiological agents of disease and as model organisms for research. The detailed discussion of eukaryotic microbial structure and function is followed by a comparison of eukaryotes and prokaryotes.