Mouse 3T3 fibroblast shown in phase contrast (left) and immuno-stained for the nucleolar protein nucleostemin (right, green).

High resolution transmission electron micrograph of a portion of the macronucleus of Opercularia coarctata containing irregularly shaped heterochromatin bodies and elliptical nucleoli. Ribosome-like p...

Fluorescence images showing the distribution of GFP-ALADIN, a WD-repeat protein that is mutated in the human triple A syndrome (green), and the nucleoporin Nup358(red)within the nuclear envelope of He...

High resolution transmission electron micrograph of Halteria showing both the large macronucleus with nuclear pores, dense heterochromatin bodies and nucleolus, and the small micronucleus.

Mouse 3T3 fibroblast stained for the nucleolar protein nucleostemin (left, green) and 28S rRNA (right, red).

Transmission electron micrograph of rat liver cell showing a grazing section through the nuclear envelope and illustrating the high density of nuclear pores in cells from a 1 day old animal. The cytop...

Mouse 3T3 fibroblast immunostained for the nucleolar protein nucleostemin (left, green) and fibrillarin (right, red) marking nucleolar fibrillar centers.

Rat NRK fibroblasts in phase contrast and stained for the nucleolar proteins nucleostemin (green) and fibrillarin (red). Panels at right show merge. Rows show different stages of mitosis, from top, ea...

Transmission electron micrographs showing the unusual configuration of nucleoli in Sertoli cells, with smaller, highly dense spherical bodies flanking a large central body. Upper micrograph from guin...

Transmission electron micrographs showing the unusual nucleolar structures in Sertoli cells of ruminants, with varying numbers of vesicles and tubules; the upper panel illustrates such an organization...