FIGURE 4-29 Transmission electron microscopy of negatively stained samples reveals fine features. (a) Samples for transmission electron microscopy (TEM) are usually mounted on a small copper or gold grid. The grid is usually covered with a very thin film of plastic and carbon to which a sample can adhere. (b) The specimen is then incubated in a heavy metal, such as uranyl acetate, and excess stain is removed. (c) The sample excludes the stain, so when it is observed in the TEM, it is seen in negative outline. The example in (c) is a negative stain of rotaviruses.

[Part (c) ISM/Phototake.]