  The angle between the spin axis of the host star and the orbit of its planets
(i.e., the stellar obliquity) is precious information about the formation and
evolution of exoplanetary systems. Measurements of the Rossiter-McLaughlin
effect revealed that many stars that host a hot-Jupiter have high obliquities,
suggesting that hot-Jupiter formation involves excitation of orbital
inclinations. In this contribution we show how the passage of the planet over
starspots can be used to measure the obliquity of exoplanetary systems. This
technique is used to obtain - for the first time - the obliquity of a system
with several planets that lie in a disk, Kepler-30, with the result that the
star has an obliquity smaller than 10 degrees. The implications for the
formation of exoplanetary systems, in particular the hot-Jupiter population,
are also discussed.
