“…Let (Y, o) be a pointed algebraic variety over the complex numbers. Its pro-unipotent fundamental group π 1 (Y ; o) is a rich source of links between the topology, geometry and arithmetic of the variety: see for example the works of Bloch [Bl77], Chen [Chen], Deligne [De], Drinfeld [Dr], Hain [Hain3] and Kim [Ki] and the references therein. Among these developments, the contributions of Carlson, Clemens and Morgan [CCM], Harris [Har] and Pulte [Pu] in the eighties exhibited examples where the values of Chen's iterated integrals -which provide an explicit description of the underlying mixed Hodge structure of the de Rham realization of π 1 (Y ; o)-coincide with the Abel-Jacobi images of a suitable nullhomologous cycle on Y or on some other variety that one may naturally construct out of Y .…”