Presented below is a photomicrograph of a down feather, showing loose-webbed barbs rising from the tip of a very short shaft. This digital image was captured with the DXM 1200 ACT-1 control software in single-image acquisition mode utilizing fluorescence illumination.

Feathers have an exquisite beauty and functionality that has captured the attention and imagination of people for centuries. They are specialized epidermal growths, formed by papillae that are composed of keratin, lipids, and pigments that give them their brilliant colors. Keratin is an ideal material for feathers because it is lightweight and flexible, yet strong enough to form a structure that can withstand the rigors of flight.

Feathers can be divided into several categories. Contour feathers are found on the wings and backs of birds, while down feathers are usually placed underneath the contour feathers to provide insulation for the bird. A primary feature present in all feathers is the large stem (termed the "rachis" or "quill") centrally located that provides a "backbone" around which the feather is constructed. Extending from both sides of the quill is a linear cluster of barbs containing a majority of the feather's pigment. Together, the barbs and the quill constitute the body or vane of the feather. Branching at a 40-degree angle on each barb is a network of barbules with interlocking hooklets that provide both stiffness and flexibility to the feather. These hooklets allow a split vane to be resealed making it whole again.