When I hear the word transparency, I think of the thin sheet that is placed on a projector and written on. This pastry technique is similar, but edible.
Using pectin (a gelling agent used when making jams or jellies) and a low temperature oven, one can make flavored "glass" sheets.
Example: At the restaurant Alinea, chef Grant Achatz makes a raspberry transparency dusted with yogurt powder.
Raspberry juice is cooked with water and pectin (1 gram of pectin to 70 grams raspberry juice). The mixture is poured onto an acetate sheet. An acetate sheet is just an extremely thin plastic sheet, commonly used for chocolate work. The sheet is then placed in a 105 F oven for 8 hours, until the raspberry sheet has a glass like consistency.