Individual tachyzoites of T. gondii in a fibroblast cell. Left: the microscopic image as seen by differential interference contrast microscopy (with the fibroblast nucleus on the bottom right). Right: the same under fluorescence light illumination whereby the green structures are mitochondria of the fibroblasts; the yellow/red structures are those of the parasite and the light blue stained “dots” represent an organelle (called apicoplast) related to plant plastids. Source: Frank Seeber, RKI (Crawford et al. 2006 EMBO J.)