Driving phase transitions in materials with light on the ultrafast enables rapid control over material properties. Ultrafast spectroscopies have advanced so that we can track these events with attosecond temporal resolution. However, in general, time-resolved measurements are spatially averaged, so we do not know what is happening spatially. In (or close to) equilibrium, we know that phase transitions are often heterogeneous, with both phases existing on different length scales, but currently we do not know what happens on ultrafast timescales as we lack probes that can measure in time and space. In this talk, I will present our work where we exploit the power of X-ray lasers (XFELs) to study light-induced phase transitions on a range of length scales. I will show how we can track and control how the distribution of atomic positions changes during the phase transition. How we can use X-rays to measure phase transitions at a surface of a crystal, and how we can use resonant soft X-rays to image dynamic heterogeneity on the nanoscale.