A classical theorem of Hasse-Minkowskii asserts that a quadratic form over a number field represents zero nontrivially if it does over the completions of the number field at all its places. There are general results on Hasse principle for homogeneous spaces under connected linear algebraic groups and their obstructions over number fields. We explain similar questions of Hasse principle over function fields, with special reference to function fields of p-adic curves. There are interesting open questions when one passes to function fields of curves over number fields.