When scientists are looking into space, the more they can see, the easier it is to piece together the puzzle of the cosmos. The James Webb Space Telescope’s mirror blanks have now been constructed. When polished and assembled, together they will form a mirror whose area is over seven times larger than the Hubble Telescope’s mirror. JWST’s mirror is made up of 18 mirror segments that form a total area of 25 square-meters when they all come together.
https://www.nasa.gov/vision/universe/starsgalaxies/mirror_size.html