For 25 years, certain California inmates held in isolation were banned from sending personal photographs of themselves to friends and family.
Officials said that prison gang leaders were using them as a kind of 'calling card'.
But with no way to track what their loved ones look like - many of the men in prisons like Pelican Bay became all but invisible to relatives living hundreds and even thousands of miles away.
Prison officials have since eased those restrictions and hundreds of families are seeing the faces of their relatives - some for the first time in decades.
KQED's Michael Montgomery spent nearly a year with the Center for Investigative Reporting gathering photos, letters and other artifacts, tracing the solitary lives of men detained at Pelican Bay.
You can see the old, and new, photos of some of Pelican Bay's isolation inmates on the Center for Investigative Reporting's 'Solitary Lives'.