Soluble collagen comes from animals and fish. It has a large molecule size, meaning it doesn't get absorbed into skin.

Instead, it sits on top of skin as a humectant to improve skin hydration. It has incredible water-binding properties and creates a water barrier on skin that prevents evaporation.

Water. It's the most common cosmetic ingredient of all. You'll usually see it at the top of ingredient lists, meaning that it makes up the largest part of the product.

So why is it so popular? Water most often acts as a solvent - this means that it helps dissolve other ingredients into the formulation.