English: Picture of the gamma-ray microscope described in Heisenberg's 1927 paper on the uncertainty principle ("Über den anschaulichen Inhalt der quantentheoretischen Kinematik und Mechanik". Zeitschrift für Physik (43): 172–198.). The blue circle is the particle, the green wave is the incoming gamma-ray and the red wave is the gamma-ray scattered up into the aperture angle θ of the microscope (depicted as solid black lines). The uncertainty in the particle position is Δx, as shown.