Color-enhanced transmission electron micrograph of a section of a interphase nucleus of Euglena (orange). The central nucleolus has clear internal tracks, involved in synthesis of ribosomes. Heterochromatin appears as granular areas, some attached to the inner nuclear membrane. These are actually sections of chromosomes which remain permanently condensed in all euglenoids. The granular nucleoplasm is delimited from the cytoplasm (yellow) by the two-membraned nuclear envelope. The cytoplasm contains ribosomes and portions of mitochondria (blue) and chloroplasts (green). Magnification 8,500x when printed at 8" x 10".