Congo Red has been used as a common qualitative staining method for the identification of amyloids in vitro and in tissue sections. Congo Red Maleimide is an excellent thiol-reactive building block to develop Congo Red-based amyloid probes. It readily reacts with peptides, antibodies and other thiol-containing biomolecules such as thiol-modified oligos. The investigation of the amyloid formation is currently one of the most important tasks in the neurological field. Research in this area involves not only understanding how amyloidosis develops and how to prevent amyloid plaque formation but also investigating functional amyloids. In amyloidosis diseases, amyloids can be detected in the kidney, liver, brain and other human and animal organs. The development of neurodegenerative human diseases, such as Alzheimer’s disease and Parkinson’s disease, is probably the consequence of accumulation of insoluble amyloid plaques in the nerve tissue.