First things first: You want it to be healthy. It all starts off with eating a balanced diet filled with proteins, omega-3 fatty acids, and vitamin D(nuts, eggs and salmon are good). If you’re dealing with extremely chronic thin hair you can take a supplement with zinc and biotin to promote hair growth (try Viviscal Extra Strength Dietary Supplement) or an over the counter growth booster like Pantene Expert Hair Regrowth Treatment for Women and prenatal vitamins are an excellent source for hair growth too. These vitamins could take some time like any other product. Just be patient but if none of these tend to work then I’d recommend that you see your Primary doctor or Dermatologist to get to the root of it. Stress or hormonal imbalance could be the problem that would require treatment from a professional doctor.