As we age, there are many compounds that are made in the body that are made at lower amounts with age.

For example, as we age, it's common for men to lose testosterone.

It's common for estrogen levels to increase.

It's common for women to experience lower progesterone levels.

And this affects the skin in a dramatic way.

For the skin, it's common for the skin to contain less and less cholesterol.

Cholesterol is very important for the skin because it protects the skin against the sun and against environmental insults.

So as cholesterol decreases, we tend to get skin that can't resist the ravages of these insults.

This skin that ages becomes more wrinkly and more brittle and less flexible and less youthful.

It is thought that by replacing these lost ingredients, ingredients that are found naturally in youthful skin, we can stay young a lot longer.

We call these different compounds that decrease with age "youth factors."

Youth factors decrease with age, and so we try to replace those youth factors with our serums and replenisher.

The serum itself is used in the daytime because it dries within a few seconds.

It doesn't leave your skin greasy at all because there's no oil in it whatsoever.

It contains many youth factors that go to work during the day and make your skin feel tighter and look tighter and look more youthful.

At night while you're sleeping, it's important to replenish the cholesterol and other compounds that are decreasing the diminished youth factors.

You don't want to wear the replenisher during the day because it contains biological oils.

There's no way around it.

It has to have some oil soluble ingredients in it to replenish the skin, which contain many oil compounds, oil-soluble youth factors.

Remember that replenisher does not clog pores and it won't increase acne, but when you put it on at night, it works all night to replenish those youth factors.

So that's why it's a system where I recommend you use the serum during the day and you use the replenisher at night.

That's what I do, and I think you'll agree that my skin looks pretty good for a man who's almost 50. I did not retouch this, and I am not wearing any makeup or concealer of any kind.