I review the main characteristics of structure formation in the quintes- sential Universe. Assuming equation of state w=p/\varrho =const. I provide a brief description of the background cosmology and discuss the linear growth of density perturbations, the strongly nonlinear evolution, the power spectra and r.m.s. fluctuations as well as mass functions focusing on the three values w=-1, -2/3 and -1/3. Finally I describe the presently available and future constraints on w.

PACS numbers: 95.35.+d, 98.62.--g, 98.62.Ai, 98.62.Ck