The Latin words “Corpus Christi” translate to “Body of Christ.” The Eucharist is the “source and summit of the Christian life” (Second Vatican Council, Lumen gentium, no. 11). In the Eucharist, Jesus Himself re-presents for our benefit His Sacrifice on Calvary (Luke 22:19-20; 1 Cor. 11:26-29), gives Himself to us in Holy Communion (Exodus 16:4, 35; John 6:1-14, 48-51), and remains among us until the end of the age (Luke 24:13-35; Mt. 28:18-20). He comes to us in this humble form, making Himself vulnerable, out of love for each one of us. Yet, as God Himself, the Body and Blood of Christ deserves our utmost respect and love, as well as our adoration.St. Thomas Aquinas, Hymn “Tantum Ergo” Down in adoration falling, Lo! the sacred Host we hail; Lo! o'er ancient forms departing, Newer rites of grace prevail; Faith for all defects supplying, Where the feeble senses fail. St. Francis of Assisi said, "...In this world I cannot see the Most High Son of God with my own eyes, except for His Most Holy Body and Blood." The traditional date for Corpus Christi is the Thursday after Trinity Sunday, itself the Sunday after Pentecost. Thursday was chosen because it was the day on which the Last Supper was celebrated. Many ecclesiastical provinces (e.g. United States), however, celebrate it on the following Sunday, so that more people can attend. Where it occurs on Thursday, it is a Holy Day of Obligation, that is, Catholics must participate in the Mass. Whenever the Eucharist is exposed for adoration of the people, it is placed in a sacred vessel called a Monstrance, whose clear glass permits the viewing of the Sacred Host. Such Exposition can take several forms, on the altar in a parish, for adoration and prayer, public devotions such as Eucharistic Benediction, and public processions on Corpus Christi, or at other times. In Catholic countries such processions often go throughout the city. The faithful usually sing and pray, all in honor of our Eucharistic King. This practice began in the 14th-century, and it has been promoted by popes, councils, and saints as a wonderful way to show the supreme importance of the Eucharist and the love that we have for Him. The Holy Eucharist is the greatest of the seven sacraments. The Catholic Church teaches that in the Eucharist, Our Lord Jesus Christ, true God and true man, is really, truly, and substantially, present under the appearances of bread and wine. Our Lord is not merely symbolized by the bread and wine; nor is he present only through the faith of those present. Rather, the two material things, bread and wine, are completely changed into the Body and Blood of Jesus Christ, leaving behind only their sensible appearances. Thus, through the words of consecration spoken by the priest, Jesus, without ceasing to be present in a natural way in heaven, is also present sacramentally, Body, Blood, Soul and Divinity, wherever the consecrated elements are present. The Eucharist is discussed many times in Sacred Scripture in its root meaning “to give thanks” (Ps. 9:1, Is. 12:1,4; Col. 3:17; 1 Thess. 5:18). Giving thanks, or blessing God, was the essential element of the prayers of temple, synagogue, and daily life for Israel. There are many instances, as well, in the Old Testament where the Eucharist is foreshadowed even in its sacramental forms, such as Melchizedek’s offering of bread and wine (Genesis 14:18–20), the Passover (Ex. 12:1-14), and the manna which sustained Israel until it could enter into the Promised Land (Ex. 16:13-17). Christ likewise always gave thanks to His Father for His good gifts. This is recorded especially in contexts where He anticipated the forms of new covenant worship. These include the wedding feast of Cana (John 2), changing water into wine, the two multiplication of loaves miracles (Mt. 14:13-21; Mt. 15:32-39), multiplying substance to satisfy the needs of all, and His explanation of the Eucharist in the Bread of Life Discourse (John 6). Finally, at the Last Supper He instituted the Eucharist, as the normative way of commemorating His Paschal Sacrifice on Calvary, commanding that we do this until He comes again (cf. 1 Cor. 11) . “It is called Eucharist, because it is an action of thanksgiving to God. The Greek words ‘eucharistein’ and ‘eulogein’ recall the Jewish blessings that proclaim - especially during a meal - God's works: creation, redemption, and sanctification.” (CCC 1328)