Fluorescence light microscopy has the unique ability to observe cellular processes over a scale that bridges four orders of magnitude. Yet, its application to living cells is fundamentally limited by the very rapid and unceasing movement of molecules that define its living state. What is more, the interaction of light with fluorescent probes that enables the observation of molecular processes causes their very destruction. Ultrarapid cryo-arrest of cells during live observation on a microscope now circumvents these fundamental problems. The heart of the approach is the cooling of living cells with enormous speeds up to 200,000 °C per second to -196 °C. This enables an unprecedented preservation of cellular biomolecules in their natural arrangement at the moment of arrest. In this low temperature state, molecular movement and light-induced destruction is stopped, enabling the observation of molecular patterns of life that are otherwise invisible.
