Lecithin is a powerful emulsifier widely used in foods, feeds and pharmaceuticals, which functions mainly due to its adsorption properties. Lecithin adsorbs to fat crystals at the triglyceride oil/water interface, and makes their surface more polar (observed as an increase in the contact angle measured through the oil at the interface: fat crystal/oil/water). This adsorption process is quick (less than five minutes) for relatively polar lecithins like soybean phosphatidylcholine (PC), and results in highly polar surfaces (contact angle ≈180°). Less polar lecithins give a slow adsorption (some hours) and less polar crystals (contact angle < 90°). The adsorption of different lecithins to the oil/water interface, observed as a decrease in interfacial tension, follows the adsorption pattern to the fat crystals (the more polar the lecithin the quicker the adsorption). There is a relationship between the high polarity of fat crystals and the poor functionality of lecithin in margarine (margarines spatters during frying). There is also a relationship between a high polarity of fat crystals and a high ratio of polar to nonpolar phospholipids (SPI+PA+LPC/SPE) in lecithin. The correlations migth be via aggregation properties of lecithin in the oil, which should influence both the adsorption kinetics and the structure of adsorbed layers. A monoglyceride (monoolein) shifts the adsorption kinetics of lecithin (soybean PC) to fat crystals and the structures of adsorbed layer. The reason is probably a formation of mixed aggregates between monoolein and soybean PC.