In 1508, Pope Julius II commissioned Michelangelo to paint the 12 apostles on the ceiling of the Sistine Chapel.
Four years and more than 300 images later, the ceiling of the chapel told the story of the Bible in pictures and became Michelangelo's masterpiece.
Now some physicians say Michelangelo hid a secret code in his masterpiece -- an ecclesiastical anatomy lesson.
Dr. Lynn Meshberger first noticed one mysterious image in the painting after he dissected a human brain in medical school.
"I went back to my apartment where I had received that day a book about Michelangelo," Meshberger said. "My heart was racing and I felt goose bumps. I saw the image that encompasses God is the same as the human brain."
He published his finding in the Journal of the American Medical Association. And now, some 15 years later, two Brazilian doctors say they've discovered other secrets in 34 of the 38 panels.
In one section of the master painting, Gilson Barreto and Marcelo de Oliveira say Michelangelo hid the image of the diaphragm, the heart and the aorta. In another titled "The Creation of Eve" what looks like a tree trunk, the Brazilians say is actually a bronchial tube. They also believe God's purple robe is a cross-section of a human lung.
Not everyone is buying this theory, however.
"There's absolutely nothing visible that substantiates this extremely far-fetched interpretation," said Colin Eisler, professor of fine arts at New York University. "There's that great line in the Bible, 'Seek and ye shall find.' You can find whatever you like."
So is this sublime painting really a depiction of human organs? Eisler insists Michelangelo painted exactly what he was paid to paint.
"He wasn't given carte blanche to do what he wanted for a split second," Eisler said.
But Michelangelo did make at least one personal decision -- he used his own image for the painting of Saint Bartholomew holding his own skin.