The transmission electron micrograph shows stacked annulate lamellae from a human Sertoli cell. Annulate lamellae consist of sheets of membrane containing closely packed structures resembling nuclear pores. Micrograph courtesy of Hector Chemes, Figure 163 from Chapter 4 (Nucleus) of 'The Cell, 2nd Ed.' by Don W. Fawcett M.D. A PDF copy of the accompanying chapter is available on the ASCB's BioEDUCATE website.