I'd like to introduce the ampoule I use.

This is the ampoule I use. It is called the COSRX The Vitamin C Serum, and it has a sour scent with a vitamin fragrance. I have sensitive skin, and it stings when I apply it when it is dry, so I think those with very sensitive skin should avoid it. However, since it contains vitamins, it seems to be good for the skin. It is liquid and yellow, but it seems to change to orange over time.