In this chapter, we describe the history of amyloid research and the staining of amyloid deposits with Congo red. We discuss in detail the work of two important pioneers of amyloid research, J.P. Divry and G. Romhányi. Divry first described the anisotropy of amyloid deposits induced by Congo-red staining. Romhányi analysed unstained amyloid deposits, described the submicroscopic fibrillar structure of amyloid and determined the oriented binding of Congo-red dye molecules to amyloid. Cohen and Calkins revealed the ultrastructure of the amyloid via electron microscopy. A significant turning point in amyloid research occurred when Benditt et al. found that amyloid protein A is not stable for Congo-red binding at alkaline pH values (11.5), whereas amyloid protein B retains bound Congo red under these conditions. Then Romhányi described that by using potassium permanganate treatment, combined with trypsin digestion, primary and secondary amyloid deposits can be distinguished from each other, and he showed that primary amyloid becomes resistant to this treatment. According to Per Westermark’s amyloid concept (2012), amyloid has the following characteristics: Today, 42 types of amyloids are known, according to Amyloid Forum in Heidelberg (2022). AA, AL, ATTR, endocrine and local amyloidosis and their various therapeutic treatments are described in detail.