A curly hair can also be described according to its composition and structure. A research team based in Clichy, France, and working for the cosmetics firm L'Oréal, used electron microscopy to compare straight and curly hair fibers. The former were circular in cross section and symmetrical in structure. The latter, though, had an uneven distribution of a particular type of keratin. This protein—which, along with other varieties of keratin, serves as the primary component of hair—accumulated near the inside edge of a curled hair, beneath the curve.