A coloured transmission electron micrograph (TEM) of a cell within a leaf of the moss Physomitrella patens, syn. Physcomitrium patens, The picture shows a central chloroplast (green) with starch grains (pale yellow), and two others (to edges). The blue background is the cell cytoplasm, with many small dark particles. These are ribosomes, the sites of protein synthesis. The red particles are mitochondria, which generate energy for the cell's metabolism. Small indistinct stacks of membranes (yellow) are golgi bodies, active in intra-cellular transport. P. patens is used as a model organism in biotechnology research due to its simple genome and its ability to regenerate from single cells. By introducing novel genes into the plant, it is possible to use the moss in a bioreactor to make useful products such as biopharmaceuticals. Magnification: x1400when printed at 10 centimetres tall.