Observations of supernovae within a few days of explosion provide unique constraints to the nature of their progenitors. Since 2013, as a part of my thesis, I used the intermediate Palomar Transient Factory (iPTF) to systematically study extraordinarily young supernovae. I will first provide an overview of iPTF survey design, summarize the fast turnaround discovery pipeline and then outline the rapid response follow-up. The highlights of my work are as follows: 1) We observed a strong declining UV emission from a low-velocity Type Ia supernova which is consistent with the expected emission from a supernova slamming into a companion star. Our observation evidently suggests that some Type Ia supernovae arise from the so-called "single degenerate" channel. 2) We identified the first progenitor candidate of a Type Ib supernova in the pre-explosion HST images. Our multi-wavelength observations of this young Type Ib supernova constrain its progenitor to be smaller than several solar radii and with strong mass loss. 3) We also found a peculiar hydrogen-deficient supernova which shows a double-peaked lightcurve, low peak luminosity, slow expansion velocity and fast declining. This supernova is consistent with formation of a black hole from core-collapse of a massive star. I will end my talk with prospects for this field with the upcoming Zwicky Transient Facility and adapting the fast-response system to searching for electromagnetic counterparts of advanced LIGO events.