The origin of Type Ia supernovae (SNe Ia) is still unknown. While
it is widely accepted that they result from the explosion of a white dwarf
in a binary system, we know very little about the nature of the companion
star. To reveal the true nature of SNe Ia and make more stringent use of
them in cosmology and for nucleosynthesis yields, we therefore need
stringent methods to discriminate between possible progenitor scenarios.
I will discuss some possible methods and what they have revealed.