Once the molecule has been tethered between the two beads, the unzipping experiment can start. There are two types of unzipping experiments: controlled position and controlled force. The natural way to produce unzipping with optical tweezers is at controlled position. The reason is that the position of the optical trap is a parameter that we directly control by changing the voltage of the piezos. Instead, the controlled force experiments require the activation of a force feedback. The process of unzipping looks different if the experiment is performed at controlled position or force. Thus, the data measured with the instrument depends on the type of experiment.