Invisible Woman render other people or objects fully or partially invisible too, affecting up to 40,000 cubic feet (1,133 cubic meters) of volume. She achieves these feats by mentally bending all wavelengths of visible, infrared, and ultraviolet light to bend around herself or her target without causing any visible distortion effects. According to the "Women of Marvel: Celebrating Seven Decades Handbook", Sue's retinas don't function conventionally and instead of just registering objects using reflected light, the retinas in Sue's eyes also interpolate shapes based on reflected cosmic rays, which in the Marvel Universe are always present in the atmosphere, granted usually only
Invisible ink its intended use. For example, property marking should ideally be done with ink easily read under ultraviolet light, whereas in espionage such an ink would be considered too easily detectable since a large number of letters may be screened relatively quickly using UV light. Invisible inks are inherently "insecure" against a determined and well-equipped inspector, which must be balanced against the logistical difficulty in carrying out mass-screening of posted mail. It is easier to perform large-scale undetected screening of millions of electronic communications, than to mass-screen even a small fraction of conventional mail. Apart from in dictatorships where large numbers