Let it grow! The active brow serum stimulates the natural hair growth and promises visibly fuller brows in just four weeks**. Thanks to its transparent gel texture, it's suitable for all hair colours. Beauty Tip: Through thick and thin: our brows have been through a lot. It takes a lot of patience to let them grow. After all, brow hairs only grow half as fast as the hair on your head – so that's around 5 millimetres per month. These three tips can also help: put your tweezers away, no matter how hard it is, occasionally treat your brows to a gentle peeling treatment and regularly apply a growth serum.