However, recent breakthroughs in cryo-electron microscopy (cryo-EM) and tomography (cryo-ET) are beginning to open this “black box.” For example, landmark cryo-EM studies on patient-derived tissues have overturned previous dogmas, revealing that the abundant amyloid filaments in Frontotemporal Lobar Degeneration (FTLD-FUS) are composed not of FUS, but of the distinct RNA-binding protein TAF15, establishing a new “TAF15 proteinopathy” [41]. Here, FUS is linked to frontotemporal dementia.