One day Michelangelo, entering the place where the Pieta was displayed, found there a great number of strangers from Lombardy, who were praising it highly, and one of them asked one of the others who had done it, and he answered, 'Our Gobbo from Milan.' Michelangelo stood silent, but thought it something strange that his labors should be attributed to another; and one night he shut himself in there, and, having brought a little light and his chisels, carved his name upon it. 

Michelangelo later regretted the vanity of this act, and resolved never to sign another piece of his work. 

The piece made Michelangelo famous when he was only 24. 

Thanks in part to putting his name in plain sight on the Pietà, Michelangelo's reputation grew as the public's love of the statue did. The artist lived to the age of 88, enjoying decades of acclaim and appreciation for his works. 

The sculpture has been criticized for Michelangelo's depiction of Mary. 

Some church observers sneered that the artist made her look too youthfulto have a son who was 33 years old, as Jesus was believed to be at his death. Michelangelo defended this choice to his biographer Ascanio Condivi: 

Michelangelo has long been praised for marrying Renaissance ideals of classical beauty with poses that favored naturalism. Another nod to Renaissance influence is a structure that ultimately resembles a pyramid, formed by Mary's head, flowing down her arms and to the bottoms of her robes. 

Mary's robes hide a creative compromise. 

If you look closely, you can see that Mary's head is a bit too small for her very large body. When designing Mary's measurements, Michelangelo could not impose realistic proportions and have her cradle her adult son as he envisioned. So, he had to make her—the statue's support—oversized. To play down this poetic license on her form, Michelangelo carved out sheets of gentle draping garments, camouflaging Mary's true fullness.  

The Pietà was brutally attacked. 

Michelangelo had a habit of shouting at his sculptures and even occasionally lashing out at them with his tools. But it was an unemployed geologist from Hungary who won infamy on Pentecost Sunday of 1972 by leaping over the railings at St. Peter's Basilica to attack the Pietà with a hammer. With 12 blows, Laszlo Toth knocked off Mary's left arm, snapped off the tip of her nose, and damaged her cheek and left eye. 

Its destruction was not deemed a criminal offense. 

The authorities chose not to criminally prosecute Toth for his destruction of the priceless work of art. However, a Rome court deemed him "a socially dangerous person," and committed the man to a mental hospital for two years. After he was released, Toth was deported.

Its restoration was a matter of debate. 

When a work of art is damaged in this way, its exhibitors are forced to debate what's best—leaving it as it is (like Cleveland's The Thinker that was mangled in a bombing) or altering the original to restore it. The Vatican heard three arguments on this matter. 

The first declared that the Pietà's damage was now a part of its meaning, speaking to the violence of our modern age. Others proposed that the sculpture be repaired, but with visible seams as a reminder of this grave assault. Ultimately, a seamless restoration was chosen, with the goal of making it impossible for observers to know that Toth had even touched Michelangelo's masterpiece. 

The restoration took 10 months.

Master craftsmen picked through the 100 bits of marble broken off of the Pietà and puzzled them back together. In a makeshift lab built around the statue, these workers spent five months identifying pieces as small as fingernails. Next, they used an invisible glue and marble powder to affix the pieces back onto the Pietà and filled any gaps with replacement pieces. And once the integral restoration was completed, the final step was securing the restored work behind bulletproof glass. 

This was not the first time it was behind bulletproof glass. 

In 1964, the Vatican loaned the Pietà to the United States, where it was displayed as part of the 1964 New York World's Fair. To ensure the safety of this statue, organizers erected a barrier of seven massive sheets of plexiglass that collectively weighed more than 4900 pounds. Then, to make sure crowds would safely pass by the sculpture, conveyor belt-style mobile walkways were installed. 

The Pietà's attack had an unexpected silver lining. 

During its diligent restoration, workers discovered a secret signature on the piece. Hidden in the folds of Mary's left hand was a subtle "M" believed to stand for Michelangelo.  

“As sulptor, painter, poet, architect and engineer, Michelangelo Buonarroti remains one of the most influential artists in history, as well as being the most significantly documented artist of the sixteenth century,” explains our book, 30,000 Years of Art. ”His output was immense, and his highly-charged style gave rise, in the generations that followed the High Renaissance, to the next major artistic movement in the West: Mannerism.”

Michelangelo establish a combination of his painting style with his sculpture. This creative style evokes the beauty of the curve, as in the golden mean or sacred ratio. It started a form known as Mannerism. Thus Mannerism, ‘the stylish style’ is one that strove towards an extreme refinement and elegance in painting, sculpture and printmaking as well as in architecture and the decorative arts.”

Mannerism was an art style in late 16th century Europe characterized by spatial incongruity and excessive elongation of human figures.