Type Ia supernova (SN Ia) explosions are among the most energetic events observed in the Universe. They appear to be good cosmological distance indicators due to their high luminosities and remarkable uniformity, and thus are used for determining cosmological parameters. They are also a key part of our understanding of galactic chemical evolution owing to the main contribution of iron to their host galaxies. However, several key issues related to the nature of their progenitor systems are still not well understood. This will directly affect the reliability of the results of the current cosmological model and the galactic chemical evolution model.