X-ray free electron lasers such as the Linac Coherent Light Source (LCLS) at SLAC provide extremely short X-ray pulses with much higher intensity than previously possible. This has enabled fundamentally new studies of matter with X-rays, as well as X-ray-matter interaction. In this talk, I will discuss the power of X-rays for probing matter, focusing on the use of lower energy 'soft' X-rays. Soft X-rays do not have the penetrating power of hard X-rays, but have access to many important element-specific resonances, making them a powerful probe of electronic structure with elemental specificity. I will then overview the new opportunities in X-ray science provided by LCLS and highlight some recent example experiments.