Given the interpretation of classical periods as matrix coefficients arising in the comparison between singular and de Rham cohomology of complex algebraic varieties, it is natural to view as a p-adic analogue the comparison between etale, crystalline, and de Rham cohomology of algebraic varieties. We describe some new results and perspectives on p-adic comparison isomorphisms emerging from recent developments in the theory of perfectoid spaces. These include a new direct cohomological realization of the crystalline comparison isomorphism (by Bhatt-Morrow-Scholze), and the discovery of "abstract instances" of comparison isomorphisms corresponding to as-yet-unknown families of motives over Shimura varieties (by Liu-Zhu).