The unique architecture of Kiehl's formula is constructed to house the concentrated calendula serum ingredients within the water phase. On application, the serum infusion transforms and delivers hundreds of micronized calendula petal parts and calendula extract directly to the skin. Before the whole calendula petals are added to the formula for processing, they are first steeped at a high temperature for 10 minutes. The whole petals are steeped and mixed at the same time. During mixing, the petals become crushed into hundreds of micronized petals—visible only under a microscope.