The biggest trend in hair these days is no trend at all. Gone are the days of the iconic hairstyle—Dorothy Hamill's sassy bob, Farah Fawcett's flirty flip, Bo Derek's cornrowns, and The Rachel. Even The Thatch—Margaret Thatcher's immovable helmet of hair—is said to be making the red carpet rounds. Today, a stylish woman could make any of these looks work

First, though, your hair must be healthy. (Men, this goes for you, too.) To keep your hair in top form, it's helpful to know a little about its composition and growth.

Hair Composition and Growth

Hair follicles are tiny pockets of epidermal cells in the dermis of the scalp and elsewhere on the body. (The epidermis is the top layer of skin, and the dermis lies beneath it.) Only the palms of the hands and soles of the feet are hairless. Hair is formed by a cluster of cells at the base of each hair follicle. This cell matrix is nourished by a blood supply from capillaries in the papilla, a structure nestled in its center. As cells in the matrix divide, they push upward out of the follicle.

The portion of hair within the follicle is called the root, and the visible portion outside the follicle is called the shaft. A cylindrical (round) shaft produces straight hair, and a flat shaft produces wavy or curly hair. Pigments in the hair shaft make our hair chestnut brown or strawberry blonde or fiery red. As we age, we lose the ability to produce this pigmentation, and some or all of the hair turns white. Gray hair isn't really gray; it's an optical illusion produced by the intermingling of pigmented and unpigmented hairs. The fewer pigmented hairs there are, the more silvery gray the hair looks. The more pigmented hairs there are, the more the hair takes on a salt-and-pepper look.

Hair Care

Hair grows about five inches per year. Even rocker chick styles should be trimmed every six or eight weeks to keep the hair healthy. Bleaching to lighten hair and dyeing to darken or change its color are different processes. Bleaching removes pigment, whereas dyeing adds it. Sebaceous (oil) glands in each hair follicle naturally lubricate the hair shaft, but heat and chemical processes like bleaching can dry it out. If you color your hair, take care not to overprocess it, which can dry out the hair shaft and make it vulnerable to breakage.

Let your hair air dry, or use a warm—not hot—blow dryer. Don't hold the dryer in one spot for more than a few seconds. Likewise, if you use a curling iron or flatiron, avoid the hottest settings and don't leave the plates or barrel in prolonged contact with the hair. Hot rollers must be left in several minutes in order to set. If you use hair accessories, choose ones that won't damage your hair. Uncovered rubber bands will cause serious breakage in a hurry. Some barrette clasps or hinges and the teeth on headbands can do the same.

Use a shampoo that leaves your hair feeling clean and silky, but not heavy, greasy, or filmy. Stay away from cigarette smoke and other strong odors to keep it smelling fresh. Scaling of the scalp can be treated with an over-the-counter or prescription dandruff shampoo. If you have dry or flyaway hair, use a small amount of conditioner to tame it. It's not necessary to pay big bucks for salon hair care products—store brands do just fine.