In principle, the order of products should always be from water-soluble and thin-bodied
(serums, gels, concentrates) to fat-soluble and thick-bodied (creams and oils).
However, one must take into account individual differences in the "storage capacity" of the
skin, because not everyone can absorb the same number of products at the same time.
If a product is not absorbed even after a longer waiting time, this is usually a sign that the
skin could no longer (fully) absorb the product and then you should omit a step if necessary,
or reduce the amount of products somewhat.