The intercellular lipids in the outermost skin layer, the stratum corneum, play a vital role in skin barrier function. They act to contain the water inside our bodies, stopping us from fatal levels of dehydration, and they prevent harmful chemicals or infectious organisms from crossing through the skin. Understanding the composition and structure of these lipids is important for many applications, including treating skin diseases, improving skin resistance to irritation and infection, and protecting skin lipids from damage from chemicals, UV light and gaseous pollution. The way intercellular lipids are packed and organized in the stratum corneum is absolutely vital for their function. Using unique spectroscopic techniques, TRI is able to explore these lipid packing arrangements. Changes in lipid packing in diseased skin, or in skin exposed to various insults (chemicals, sunlight) can be analyzed, and the protective or repair effects of various skin treatments can also be assessed.