Please help! what is the active ingredient in latisse (bimatoprost) that makes lashes longer and darker?

Bimatoprost: This is a solution of an anti-glaucoma prostaglandin inhibitor which has been found to grow lashes and make them darker. The generic name of the product is bimatoprost and the trade name is Lumigan.

Latisse (bimatoprost): Bimatoprost is a prostaglandin analog/prodrug used topically as eye drops. The lash growth is a side effect discovered when the drug was used to treat glaucoma. There can be unwanted side effects including darkening of the iris color and dark circles around the eyes.