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Fracture of nanosize contacts formed between spherical probes and flat surfaces is studied using an atomic force microscope in an ultrahigh vacuum environment. Analysis of the observed deformation during the fracture process indicates significant material extensions for both gold and silica contacts. The separation process begins with an elastic deformation followed by plastic flow of material with atomic rearrangements close to the separation. Classical molecular dynamics studies show similarity between gold and silicon, materials that exhibit entirely different fracture behavior at macroscopic scale. This direct experimental evidence suggests that fracture at nanoscale occurs through a ductile process.