Lock styles of the rich and famous.

So you want stick-straight hair like Angela (Claire Danes) from My So-Called Life. Or curls like 90210's Steve Sanders (Ian Ziering). fake Hollywood figureheads who change their look week to week, you too can achieve a stylin' new hairstyle. The key: Break and remake the chemical bonds that give your locks their "shape."

See, hair (like all other matter) is made of atoms,the smallest units of any chemical element. And the way those atoms are linked together, or chemically bonded, determines whether your hair is curly or straight.

BONDS HAVE MORE FUN

Actually, it's the tiny parts that make up atoms that hold the key to bonding-specifically, the negatively charged electrons, which orbit the atom's positively charged nucleus (center), says science teacher John Signorelli.

Like TV stars who never have a hair out of place, atoms are very particular about the way their electrons are arranged. They always "like" to have a certain number in the different energy levels around the nucleus. But like the rest of us mortals, whose hair gets blown in the wind, most atoms don't have the "magic" number.

LINKING LOCKS

That's where bonding comes in. An atom with too many or too few electrons will give, take, or share its electrons with other atoms. This bonding between atoms makes molecules - groups of atoms that stick together. (Think about the bond you form with a good hairstylist when you find one!)

Whether short like Brandon's (Jason Priestley) or long like Blossom's (Mayim Bialik), hair is made of long chains of protein molecules called polymers - which are made of many smaller buildingblock" protein molecules linked end to end. You can think of the building-block molecules as the cars on a long polymer train, says Signorelli.

In hair, the polymer chains line up next to each other - like trains on parallel tracks (see diagram, right). And new bonds form between the molecules in the polymer chains. It's as if people on one train were holding hands with people on the other train through the windows.

There are two ways the molecules in adjacent polymer chains can link up: sulfur-to-sulfur bonds, which are very strong, and weaker hydrogen bonds (which are really just an electrical attraction).

If the two hair polymer "trains" line up so that there are lots of sulfur-to-sulfur and hydrogen bonds between adjacent cars, the trains will stay straight. The result: superstraight hair.

But imagine this: Say the first car on one train is bonded to the first car on the other. Then a sulfur atom on car 10 "wants" to share electrons (bond) with a sulfur atom from car 30. What happens? The whole train loops around so the two cars can meet up. Result: curls!

BOND BREAKERS

Now that you know all this chemistry, you know the key to achieving a new star-studded look: Break and rearrange some of your hair's bonds. But how? Not with your bare hands, says Signorelli. To get bonded atoms apart, "you need some form of energy, like heat or chemicals," he says.

The chemicals don't have to be very strong. Just think of what happens on The Simpsons when Marge takes a bath: She emerges from her tub with long straight blue locks. That's because water molecules break hair's weak hydrogen bonds, uncoiling some of the loops. When hair dries, the hydrogen bonds reform; the curls return (with a little help from cartoonist Matt Groening, in Marge's case).

To make a change that stays when hair dries, try using heat. Tia and Tamera Mowry from Sister, Sister, for instance, could blow-dry their curly hair straight by brushing it and holding it long enough for new bonds to form. And if Margaret Kim (Margaret Cho) from All American Girl wants curls, she can use a curling iron to break her straight hair's hydrogen bonds, and allow new bonds to form in the curled shape.

PERMANENT CHANGES

Still, these changes are a big washout the next time your hair gets wet. If you want to make a more "permanent" change, you'll have to use stronger chemicals. That way you'll have enough bond-breaking energy to break the strong sulfur-to-sulfur bonds.

To give you a "perm" or bodywave, for example, stylists would first roll your hair on curlers. Then they use strong chemicals to break both the hydrogen and sulfur bonds. Another chemical is needed to stop the bond-breaking process. This neutralizer allows new hydrogen and sulfur bonds to form while the hair is still curled around the rollers. Since the newly formed sulfur bonds can't be broken with water or heat, the perm won't wash out.

Chemical hair straightening works basically the same way, except the hair is held straight after the sulfur bonds are broken so that new sulfur bonds form in the straight shape.

If your locks end up looking nothing like prime-time hair, don't worry. "Permanent" doesn't really mean permanent. Eventually your hair will grow out-in its original shape. And just like your favorite TV star, you can start messing with it all over again.

SPLITTING HAIRS

Do "perms" weaken hair? Try this to find out.

WHAT YOU NEED:

tape * several strands of different type of hair (e.g., naturally curly, straight, permed, color-treated) * box of large paper clips * balance

WHAT TO DO:

For each type of hair, find the average weight a single strand can hold:

1. Loop one end of hair through an opened paper clip and tape as shown.

2. Tape other end of hair to table.

3. Gently add paper clips, one at a time, to opened clip until hair breaks (make sure hair didn't just slip from the tape!).

4. Weigh paper clips (minus the one that broke the hair).

5. Repeat several times with strands of the same hair type and calculate an average "carrying capacity" for that hair type (total weight from trials[divided by] number of trials).

6. Repeat for other hair types.

CONCLUSIONS:

Which hair type is strongest? Weakest? Can you explain?