Eucharistic miracle is any miracle involving the Eucharist, regarding which the most important Christian denominations, especially the Catholic Church, teach that Christ is truly present in the Eucharist, which is by itself a Eucharistic miracle; however, this is to be distinguished from other manifestations of God. Eucharistic miracles are most known and emphasized within the context of the Catholic Church, which distinguishes between divine revelation, such as the Eucharist, and private revelation, such as Eucharistic miracles.
In general, reported Eucharistic miracles usually consist of unexplainable phenomena such as consecrated Hosts visibly transforming into myocardium tissue, being preserved for extremely long stretches of time, surviving being thrown into fire, bleeding, or even sustaining people for decades. In the Catholic Church, a special task-force[1] or commission scientifically investigates supposed Eucharistic miracles before deciding whether they are "worthy of belief," in order to differentiate real Eucharistic miracles from cases of contamination by bacteria, such as Neurospora crassa or Serratia marcescens.
As with other private revelations, such as Marian apparitions, belief in approved miracles is not mandated by the Catholic Church, but often serves to reassure believers of God's presence or as the means to "send a message" to the population at large.[citation needed]
The Catholic Church differentiates between true miracles and occurrences that are explainable by natural causes. For example, in 2006, the Roman Catholic Diocese of Dallas gave over a Eucharist host that turned red while in a glass for the analysis by two University of Dallas biology professors who concluded it was naturally explicable, as Bishop Charles Victor Grahmann wrote that "… the object is a combination of fungal mycelia and bacterial colonies that have been incubated within the aquatic environment of the glass during the four-week period in which it was stored in the open air."[2] In contrast, with regards to the Eucharistic miracle at Sokółka in 2008, "The results of the testing by Professor Maria Sobaniec-Łotowska (from the Department of Medical Pathomorphology, Medical University of Białystok (UMB)) and by Professor Stanisław Sulkowski (from the Department of General Pathomorphology, UMB) are consistent and indicate the presence of human heart tissue with specific pathomorphological changes."[3] The professors wrote in an academic article that "the tissue fragments observed under the microscope undoubtedly belong to the human heart and look as if the sample had been taken from the heart of a living person in agony."[3] Further details in the article were provided that affirmed the presence of heart muscle, negating a bacterial explanation: "Important evidence that the tested material is the muscle of the human heart was mainly the central arrangement of cell nuclei in the observed fibers, which is a characteristic phenomenon for this muscle. (...) in the electron microscopic examination, clear outlines of inserts and bundles of delicate myocardium were visible."[3]