X-ray free-electron lasers (xFELs), the new generation light source, had been proved to be very powerful tools to investigate matter structures and dynamics at impressive spatial and temporal resolution, since several facilities all over the world came into operation (and more are under construction). Many beautiful experiments in the field of imaging had been performed using xFELs. In this talk, some of them will be selected to illustrate why and how to use xFELs for imaging, and the related challenges as well. There are also large amount of ongoing efforts on developing imaging methods. I will present some, as far as I understand (with personal preference). This talk will be ended with a brief introduction to the newly online European XFEL (Hamburg,Germany) and its progress.

Dr. Fenglin Wang is a Postdoc in Henry Chapman's group, CFEL, DESY. He studied PhD in Edgar Weckert's group in DESY, and received the degree in University of Hamburg in 2010. After that, he joined in Henry Chapman's group as a Postdoc. In 2013-2016, he received "Peter Paul Ewald fellowship", supported by VolkswagenStiftung(德国大众基金会), for independent researches. Meanwhile, he was also hosted by Phil Bucksbaum, and spent two years in PULSE institute at SLAC, Stanford. Dr. Wang works in the fields of coherent diffraction imaging using XFELs, MD simulations of XFEL radiation damage, and developing imaging models and algorithms.