Results and perspectives of young stellar object long look programs

Both Chandra and XMM-Newton have performed long look programs for studying the YSO physics. I will discuss recent results on the controversial issue of Class 0 YSO X-ray emission, the observational evidence of magnetic funnels interconnecting the YSO with its circumstellar disk and the Fe 6.4 keV fluorescent line emission and its origin. While recent results of the XMM-Newton DROXO program challenge the ``standard" interpretation of the Fe 6.4 kev line origin as due to photoionized fluorescing disk material, the discovery of X-ray excited Ne 12.81 μm line is a clear evidence of the interaction between X-rays and disk material. Future long look observations with XMM-Newton are required to clarify the X-ray effects on YSO disk.