X-ray emission from supernova remnants provides us with probes to high energy phenomena such as acceleration of cosmic-ray particles and nucleosynthesis in supernova explosions. In this talk, I will present some of recent results that I, with my students and collaborators, obtained from observations with Suzaku, Chandra, XMM-Newton, and NuSTAR satellites. I will mainly cover results related to particle acceleration and over-ionized plasma in Galactic supernova remnants. I will also talk about expectations brought about by high resolution spectroscopy with future X-ray observatories such as XRISM, which is scheduled to be launched in 2021.