The foundations of Marian devotion (or piety) can be found in the Gospels themselves.
When we read the Gospels attentively, we notice the veiled presence of the Virgin of Nazareth all along, although she often stays in the background. However, Mary's role is reported very explicitly in the Gospels at certain decisive and crucial moments in the life of he Son, Jesus, the Word of God. For this very reason, Catholic and Orthodox Christians are not alone in honoring the Mother of Jesus. All persons who recognize the Bible as a sacred and founding text turn to Mary with honor and respect.
It is obvious that this respect for the Mother of God has particular force and scope in the Church, which has prayed to Mary since the dawn of its Christian faith, using the Angel Gabriel's very words in the Scriptures, the words of the "Ave Maria," known universally and said by Christians all around the world! The Rosary, the Magnificat, as well as popular prayers in praise of Mary and hymns such as the Akathist Hymn are the oldest prayers drawn from the universal heritage of Marian devotion in the Church.
Marian devotion is united to the Church's spiritual life
This treasure of piety is of course expressed in a myriad of ways in the universal Church: novenas to Mary, religious objects (statues, images, Rosary beads), certain periods of the week or the liturgical calendar, places of worship (chapels, sanctuaries, basilicas or cathedrals) that are dedicated to the Virgin Mary. All this as well as the consecration to Mary proposed by different spiritual families who have chosen Mary as a life role model throughout Christian history are enough to show the extent to which Marian devotion is united to the spiritual life of the Church.
There has been a renewal of Marian piety since the Second Vatican Council. Let's not forget that it was precisely during the Council, on November 21, 1964, that the Pope Paul VI magisterially proclaimed Mary "Mother of the Church." Similarly, the Second Vatican Council reaffirmed the importance of popular piety by confirming the legitimacy of sacred images of Christ, the Virgin Mary and other saints, facing certain tendencies which aimed to have them eliminated from shrines.
That's because Marian piety—the devotion to the Virgin Mary—does not come from sentimentalism but from true love for the One who is Mother and role model, and who leads all men women and children to encounter Jesus Christ. Filial piety toward Mary Mother of Jesus gives a Christian rise to make "the firm decision to imitate her virtues" (Saint John Paul II).