Transmission Electron Micrograph (TEM) of a portion of the nucleus, rough endoplasmic reticulum, and polysomes (ribosomes not attached to endoplasmic reticulum). New proteins are assembled in the channels of the endoplasmic reticulum as they are being made. From here the membrane- bound proteins are transported to the next processing step until they are complete membrane-bound protein packages. Magnification: 20,000x @ 8 x10 inches.