An electron micrograph showing a portion of the single chloroplast of the unicellular green alga Chlamydomonas, an organism extensively used in the Siekvevitz/Palade laboratories at the Rockefeller to study chloroplast membrane biogenesis. These organisms could be grown in large cultures in the dark then, when exposed to light, rapidly and synchronously developed chloroplasts. The characteristic stacked thylakoid membrane pairs are clearly seen. Image made available by James D. Jamieson and the Department of Cell Biology, Yale University School of Medicine.