This letter reports the observation of the vacuum tunnel gap between two conductors using a high resolution transmission electron microscope. A 2.5 mm square micromachined tunneling microscope chip has been fabricated with a minimum feature size of 0.4 &mgr;m. The chip fits into a modified side‐entry type transmission electron microscope holder. The tunnel gap is controlled by a purpose‐built feedback controller. The micromachines work reliably during observation of the tip apex in a transmission electron microscope, allowing the voltage and current to be changed while the tunnel gap is observed. ©1995 American Institute of Physics.