In this essay, the author presents a short review about the emergence of memorial museums, among the general context of history museums in the 20th Century. Emphasis is made pm the different political and academic transformation of the second half of the mentioned century, with the aim of identifying their impact on the process of musealization of the past. The memorial museum is analyzed, and also commented along with the ideas of other academics, to elucidate what defines it, what differentiates it from others and how we can assume that it represents a new category of history museums.