Complex sentence: Emulsions with different structures were made for other applications, such as direct positive emulsions, which has internal fog center built in to the emulsion, which is bleached by photoholes generated upon exposure.
Split into simpler sentences: Emulsions with different structures were made for other applications, such as direct positive emulsions. Direct positive emulsion has fog center built in in the core of the emulsion, which is bleached by photoholes generated upon exposure.