1. Origin of the elements  Which reactions  Which physical conditions  Which astrophysical sites  Which quantities Yields depend on reaction rates, M, Z, treatment of convection, Mass loss, V rot, B magn, Interactions in close binaries, Explosion mechanism Explosive nucleosynthesis 1D-3D models Nomoto et al. 2013 (ARAA) Evolution of stellar systems Part of history hidden in the abundances of the elements.

2. How to constrain the yields? INDVIDUAL STARS  Check of in situ processes (WR)  Composition of the ejecta of Supernovae  Asteroseismology  Unaltered surface composition of stars composed from ISM enriched by one or two nucleosynthetic events or a restricted mass range of stars like EMP halo stars, CEMP stars  General properties of stars COLLECTIVE EFFECTS  ISM abundances (in primordial galaxies) Nomoto et al. 2013 (ARAA)

3. STRIKING OBSERVATIONAL FACTS (EMP STARS) 1) Scatter: different according to the elements considered Cayrel et al. 2004 2) No sign of Pair Instability Supernovae 3) Important amount of primary nitrogen 4) More carbon, less oxygen produced at low Z ? 5) CEMP, CRUMP (no, r, s, r and s) 6) The O-Na, Mg-Al anticorrelation in globular cluster stars 7) Helium-rich stars in globular clusters Israelian et al. 2004, Centurion et al 2003Spite et al 2005Norris et al 1997 Mc William et al 95; Barbuy et al. 96; Christlieb et al. 04; Frebel et al. 05; Plez & Cohen 05 Gratton et al 2004; Piotto et al 2005 Observations:

4. IN THE FIELD IN GLOBULAR CLUSTERS IN THE HALO TWO KINDS OF CHEMICALLY PECULIAR STARS STARS MADE OF H- and He-burning productsH-burning products Norris et al 97 Gratton et al. 2004 Large scatter

5. SAME MASS: 60 M sol, SAME V ini =800 km s - 1 Z=0.00050 Z=0.00001 Slow wind: MS Only enriched in H-burning products Slow wind: YSG enriched in H- and He-burning products

9. WW95 CL04 Netal06 V=0, Hetal05 V=300, Hetal05