Eucharistic devotion refers to a number of religious practices surrounding the Blessed Sacrament outside the celebration of Mass. These practices include private visits to the Blessed Sacrament, processions with the Blessed Sacrament, Exposition of the Blessed Sacrament, and Benediction of the Blessed Sacrament.

Eucharistic devotion presupposes faith in the Blessed Sacrament as well as the reservation of the Blessed Sacrament outside Mass, a practice that can be traced at least to St. Justin in the 2^nd century. For centuries the practice inspired respect for the Blessed Sacrament, but it did not give rise to special religious practices until the 13^th century, when several factors contributed to their emergence.

Theological controversies over the reality of Christ’s presence in the Blessed Sacrament invited private and public expressions of faith. Developments in the liturgy itself encouraged such manifestations by emphasizing the elevation after each consecration. By excluding the faithful from participating in the cup, the liturgy also gave greater prominence to the host.

The earliest Eucharistic devotion consisted in private visits to the Blessed Sacrament. These became popular at the beginning of the 13th century. Later in the same century public processions with the Blessed Sacrament originated in connection with the Feast of Corpus Christi in the city of Liège, and the practice soon spread throughout Europe.

Exposition of the Blessed Sacrament began at the end of the 14^th century as an extension of the feast of Corpus Christi in response to popular piety. Benediction of the Blessed Sacrament arose in the 14th century as a conclusion for Compline and Vespers. A precedent for this practice had been set in the Benediction stations that became part of the Corpus Christi processions.

The primary spiritual attitude in all these devotional practices was adoration, but they also invited other basic attitudes inspired by the Eucharistic liturgy, especially faith, charity, hope, thanksgiving, reparation and petition.

In the course of the centuries Eucharistic devotions acquired such importance as to displace the Mass in popular religiosity. This displacement tended to obscure the relationship between the devotional practices and the liturgical celebration from which they had sprung.

Vatican II and the decrees implementing it called for a simplification of the Eucharistic devotions and the elimination of elements that distracted from the Eucharistic sign of bread. It also required that they not distract from the celebration of Eucharist, that the Blessed Sacrament be presented in such a way that its relationship to the Mass would be clear, and that the attitudes of the faithful be inspired by the Eucharistic liturgy and its meaning as presented in Scripture, tradition, and the Church’s official teaching.

Accordingly, the expression of Eucharistic devotion has been greatly simplified. Exposition, for example, is done by placing the Blessed Sacrament directly on the altar with little surrounding it that would distract from the Eucharistic signs. The traditional attitudes toward the Blessed Sacrament are complemented by a search to interiorize the significance of the Mass, which the Blessed Sacrament evokes. As a result, Eucharistic devotions have become characterized by contemplation and meditation rather than by specific acts of prayer.

--Downey, M. The New dictionary of Catholic spirituality.