The Eucharist, for all of you non-Catholics, is the term for the consecrated host that is dispensed to believers at Catholic Masses. By doctrine, it can only be made from water and flour, nothing else. Here in our neck of the woods, the hosts for the surrounding Catholic dioceses are made by nuns at a small monastery in Westfield, VT.
What's so special about the Eucharist? Well, in contrast to other Christian denominations that also do Holy Communion, Catholics believe that during Mass, by the God-given power of the Catholic priest, the host and wine are being "transubstantiated" into the actual body and blood of Jesus Christ.
None of that "communion is a symbol of the Last Supper" crap that the Protestants do--we literally eat and drink Jesus. I know, sounds gross and cannibalistic, which is what I thought at first when I converted to Catholicism.
But I now realize you can't grasp the true miracle of the Eucharist until you fully believe in it... and you can't believe in it until you fully grasp it. It seems like a problem without a solution, but it works, and maybe that's the greatest miracle of all.
Eucharistic miracles come in different categories:
In every instance of the 120 or so church-investigated and confirmed Eucharistic miracles of the third kind, which happened over the span of many centuries, it turned out that the Eucharist had changed into human heart tissue, blood type AB.
The tissue also tends to be incorruptible; that means even with Eucharists that morphed in the 8th or 12th century and were kept in a box without refrigeration or preservation, modern researchers were able to examine them in a lab and find that the tissue was still fresh and not deteriorated.
This is a pretty long video, but if you're fascinated by the supernatural, as I've always been, I encourage you to watch the whole thing. The most mind-boggling revelation (to me) came toward the end of the presentation, so hang in there and you'll be amazed.