Soy foods have rising popularity in European countries, due to ecological or health benefits, lactose intolerance or allergies against milk proteins. Traditional soy food such as soymilk, tofu or yuba contains small oil droplets, which have been known for many years in botany as oleosomes or oil bodies. These oleosomes are a natural oil-in-water emulsion formed from an "oil phase" of triacylglycerides with an "emulsifier" consisting of phospholipids and unique umbrella shaped proteins called oleosins which stick into the oil phase. The exterior hydrophilic part of the oleosomes (N- and C- terminal domains) shields the phospholipids and is, because of its pH-dependent charge, responsible for the extraordinary stability of oleosomes against coalescence and creaming. At a clean air-water interface oleosomes show an interesting behavior, including their time and concentration dependent rupture followed by the formation of a stable 2D-film of its constituents. This film consisting of TAGs, phospholipids and oleosins is different in its composition according to the subphase conditions, time and surface area (compression).