This image shows the four types of mirrors on the Webb telescope. From left to right are: a primary mirror segment, the secondary mirror, tertiary mirror and the fine steering mirror. The bottom right shows an artist's conception of the Webb telescope optics with its 18 primary mirror segments. On the bottom row are the three mirror segments shown on the same scale and seen from the rear to illustrate the honeycomb structure that makes this mirrors both very light and mechanically stiff.
Credit: NASA/Ball Aerospace/Tinsley