The age of a relational structure R is the set A of finite restrictions of R considered up to isomorphism. R. Fraı̈ssé, who introduced this notion, showed that ages coincide with nonempty ideals of the poset consisting of finite relational structures, considered up to isomorphism and ordered by embeddability. Here, given two ages A ⊆ B , we study the poset D consisting of ages C in sandwich between A and B . Among other things we show that if D (...) is infinite then it contains an infinite chain. (shrink)