The Madonna is represented as being very young for the mother of an approximately 33-year-old son, which is not uncommon in depictions of the Passion of Christ at the time. Various explanations have been suggested for this. One is that her youth symbolizes her incorruptible purity, as Michelangelo himself said to his biographer and fellow sculptor Ascanio Condivi:
The structure is pyramidal, and the vertex coincides with Mary’s head. The statue widens progressively down the drapery of Mary’s dress, to the base, the rock of Golgotha. The figures are quite out of proportion, owing to the difficulty of depicting a fully-grown man cradled full-length in a woman’s lap. Much of Mary’s body is concealed by her monumental drapery, and the relationship of the figures appears quite natural. Michelangelo’s interpretation of the Pietà was far different from those previously created by other artists, as he sculpted a young and beautiful Mary rather than an older woman around 50 years of age. 
A pietà (Italian pronunciation: [pjeˈta] ; meaning “pity”, “compassion”) is a subject in Christian art depicting the Virgin Mary cradling the dead body of Jesus, most often found in sculpture. As such, it is a particular form of the Lamentation of Christ, a scene from the Passion of Christ found in cycles of the Life of Christ. When Christ and the Virgin are surrounded by other figures from the New Testament, the subject is strictly called a lamentation in English, although pietà is often used for this as well, and is the normal term in Italian.
Although the pietà most often shows the Virgin Mary holding Jesus, there are other compositions, including those where God the Father participates in holding Jesus (see gallery below). In Spain the Virgin often holds up one or both hands, sometimes with Christ’s body slumped to the floor.
3. Although he worked in Florence most of his life, Michelangelo sculpted the “Pieta” during a five-year period he spent in Rome. It was commissioned by Cardinal de Billheres.
7. Four fingers on Mary’s left were broken and restored in 1736.
A long debate ensued in the Vatican over how the sculpture was to be restored: one side argued to leave the Virgin Mary’s face disfigured, thus speaking to the violence of our modern age; another proposed that it be restored with visible seams where the repairs had been made; but it was the third suggestion, that of an integral restoration, that eventually prevailed.
LOCATION IN SAINT PETER’S BASILICA
This was the only work of Michelangelo to which he signed his name.
Michelangelo, Pieta, c. 1498-1500, marble