Histological observations were made on the penetration of hyphae of Rhizopus oligosporus into soya bean tempe and defatted soy flour. Hyphae infiltrated to a depth of similar to 2 mm in 40 hours for soya bean tempe and to similar to 5-7 mm for tempe-flour in the same time. Different staining techniques were followed, including the use of Harris＇ haematoxylin and eosin and a Grocoh methenamine sliver fungal stain. During tempe fermentation, different enzymes were produced, which included proteases, and their activities are shown. A schematic model that related endoglucanase and endoxylanase diffusion with the movement of hyphae is proposed.