The photomicrograph illustrated below is a medium-magnification phase contrast image of a stained thin section of a tobacco mosaic virus-infected tobacco leaf. Combining phase contrast microscopy with classical histological staining techniques often yields enhancement of cellular features.

Tobacco mosaic virus is a small rod-shaped RNA virus that infects crops related to tobacco, producing a green or white filiform appearance on the leaves. The virus is transmitted via contact (tools, clothes, etc.) during cultivation and maintenance of the crops. It is also present in seeds, root water, and plant debris, so great care must be taken to avoid spreading the infection.