The Tecnai Femto ultrafast electron microscope (UEM) can enable scientists to explore events and processes that occur at the atomic and molecular spatial scale over time spans measured in femtoseconds (10−15 seconds). These include such fundamental processes as the absorption of light energy and its transformation into heat or mechanical changes (photoactuation) and the crystallization or recrystallization of materials. For the observation of reversible processes, the instrument operates in stroboscopic mode, acquiring a sequence of images much like the frames of a motion picture. For irreversible processes, such as fractures, the instrument can be operated in the single-pulse mode. The instrument can also be operated in conventional continuous-beam TEM mode.