The following example and illustration help to clarify the idea of Heisenberg's Uncertainty Principle. To see an electron, and thus determine it's position, you might use a powerful light microscope. For the electron to be visible, at least one photon of light must bounce off of it, and then pass through the microscope into your eye. A problem occurs here, as the photon transfers some unknown amount of its momentum to the electron. Thus, in the process of finding an accurately position of the electron (by making {delta} x really small), the same light that allows you to see it changes the electron's momentum to an undeterminable extent (makes {delta}p very large).