In-situ observation of tensile testing experiments at extremely low forces, yet very high load resolution (down to 1×10-5 N). The tensile speed range is 0,1 to 20 µm/s. These features, coupled with maximum stiffness of this substage, allow very accurate measurements on fibers of down to 2.5 µm diameter, and several millimeters in length. The specimens can be observed statically or dynamically at magnifications well beyond 10,000 x magnification. With the inclusion of a fine tungsten wire, that touches the specimen from underneath at 90 degrees, heating up the specimen locally is also possible.