  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 line origin as due to photoionized fluorescing disk material, the discovery
of X-ray excited Ne 12.81 micron 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.
