  We present a model of dark energy based on the string effective action, and
on the assumption that the dilaton is strongly coupled to dark matter. We
discuss the main differences between this class of models and more conventional
models of quintessence,uncoupled to dark matter. This paper is based on talks
presented at the "VII Congresso Nazionale di Cosmologia" (Osservatorio
Astronomico di Roma, Monte Porzio Catone, November 2002), and at the Meeting
"Dark Energy Day" (University of Milano-Bicocca, November 2002). To appear in
the Proc. of the International Conference on ``Thinking, Observing and Mining
the Universe" (Sorrento, September 2003), eds. G. Longo and G. Miele (World
Scientific, Singapore).
