I always doubted using yeast/fermentation product because my previous experience was not extraordinary. However, my friend convinced me that yeast/fermentation is useful for anti aging, so I thought I'd give it another try. I use this product after serum. Wait for at least five minutes until it is fully absorbed. By then my face already felt firm and toned. Afterwards I use my anti aging emulsion or cream. Make sure the product is fully absorbed before layering with other product, or it will pill up on your face and you lost the benefit.