A feather grows only at its base. There are six types of feathers: contour, flight, down, semiplume, bristle and bristle/eyelash, and filoplume. Below are examples you may see in lab:
	To the left is a contour feather. These are found over all of the birds body except the beak and scaly legs. The base provides insulation. The tips, in aquatic birds, are frizzled and repel water. They also streamline the body and increase the efficiency of flight.
	The soft and fluffly looking feather to the left is a down feather. They lie under the contour feathers and provide insulation also. Some birds, such as herons, have down feathers which turn into a fine powder. When the powder is preened into the contour feathers, it acts as a water repellent.
	To the left is a feather inbetween a down and a contour feather in structure. It is called a semiplume feather. They provide insulation.