Understanding the correlated interplay between atomic structure and electronic structure and properties is a fundamental challenge in condensed matter physics, particularly for correlated materials exhibiting strong coupling between charge, spin, orbit, and lattice vibrational degrees of freedom. Time-resolved measurements provide a new window to this problem by enabling the study of coupled interactions on time scales shorter than the underlying correlations. This talk will focus on recent ultrafast measurements of photo-induced phase transitions in transition-metal oxides, molecular complexes, and manganites in which the underlying mechanism of the phase transition is revealed by the time-scale of the dynamics. The talk will also discuss recent progress in the development and application of ultrafast x-ray techniques to the study of atomic and electronic structural dynamics in complex materials. X-rays are ideal probes of atomic structure, and offer important advantages for probing electronic structure as well (valence states, bonding geometry etc.) The application of x-ray structural probes on the time scale of a vibrational period, ~100 fs, is an important new tool for understanding complex materials.