English: Tissue section with radioactive RNA in situ hybridization followed by coating with autoradiographic emulsion, development of silver grains and hematoxylin staining. See Methods section of original paper for details.

From the original figure legend:

Localization of expression of mRNA encoding TGF-βs in ovine ovaries. Panels a and b contain corresponding light field and dark field views of a type 5 follicle from an adult ewe hybridized to TGF-β1 antisense RNA. Silver grains indicating hybridization of the TGF-β1 antisense RNA are observed concentrated in thecal (t) cells close to the basement membrane with no specific hybridization observed in either the granulosa cells (gc) or oocyte (o). Scale bar equals approximately 100 μm.