The 50th International Eucharistic Congress in Dublin (10-17 June 2012) referred to the most important dimension and aim of the Eucharist, that is building people’s communion with God via Christ in the Holy Spirit, and with one another in God. As its main goal it chose showing the outline of these issues mainly on the basis of selected documents of the Church from the period of John Paul II’s and Benedict XVI’s pontificates. The Eucharist is the source and school of spirituality of communion in all its dimensions. First Christ by the power of the Holy Spirit makes the Eucharist a place of a personal bond with the mystery of the communion of the Holy Trinity, of deepening the dwelling of the Holy Trinity in each man, and of building communion with one another in God. The Eucharist is a place of communion with others, owing to a profound unity of members of the Mystic Body in communion with Its Head. This building of a bond, started in celebration, should be continued and should consist in the actual service of love, whose aim is unifying people with God and in God (cf. John Paul II Novo Millennio Ineunte, nr 43), making the whole life more Eucharistic, that is being an expression of “spiritual service to God” (logike latreia, Rom 12,1).