Challenge: Transparency (meaning you can see the scalp, and when you lift the hair by the roots, light goes right through) and lack of volume and fullness; appears greasy.
Solution: Avoid bleach-based highlights, teasing and layers, all of which weaken the hair. Best style? The shorter, the better. “Chin length is ideal,” says Yves Durif, proprietor of the eponymous salon in New York's Carlyle Hotel. “Beyond that will show transparency.” And use a semi-permanent color, which fattens thin hair.