Millet seed extract is a natural ingredient that’s been shown to stimulate Hair Growth and make hair thicker. Millet seed extract is also a great ingredient for strengthening your hair, so you can use it in place of biotin to help your hair grow thicker. You can also find millet seed extract in supplements, hair oils and serums. Take note that this ingredient has a very strong smell. If you use it in a leave-in conditioner or hair oil, try to keep the smell to a minimum by only applying it to the ends of your hair. The best way to get past the strong odor is by taking an oral supplement.