We present a method to fabricate free-standing nanowires of various metals with controllable dimensions using λ-DNA as template for in situ Transmission electron microscopic observations. The nanowires were formed by sputter depositing or evaporating metal on DNA-strands bridging Focused Ion Beam cut narrow trenches on circular silicon heating platforms (3mm dia.). The platforms were microfabricated and compatible with any commercially available TEM holder. The nanowire dimensions (20-100 nm in diameter and 1-5 μm in length) were varied by controlling the deposition time and trench width. In situ observation during thermal annealing showed no grain growth in Al and sporadic grain growth in Au. The reason for no grain growth in Al could be due to Aluminum oxide and surface morphology. Continued annealing of the Al nanowires melted the metal leaving behind aluminum oxide nanotubes.