You might imagine a Renaissance icon like Leonardo da Vinci would be all out of surprises for us. It's been 500 years and we're still gushing over the man's body of work, which runs a staggering gamut from invention to sculpture to science to literature.

We're talking about everything from detailed renderings of human anatomy to the parachute to a tank design that predates World War I by 400 years.

The LAst Supper by Leonardo da Vinci 'The Last Supper' by Leonardo da Vinci in the refectory of the Convent of Santa Maria delle Grazie. (Photo: PrakichTreetasayuth/Shutterstock.com)

Did we mention he was a pretty good painter?

And yet, there are still so many hidden angels in the architectural wonder that was da Vinci's life. Here are just a few:

1. Even his hair gets rock-star status

If you think da Vinci may finally be starting to lose his luster, look no further than the scientific stirrings occasioned by a single lock of hair. While a DNA test is pending, Italian researchers are buzzing over the possibilities behind a strand of hair from a private collection in the U.S. bearing the very suggestive tag, "‘Les Cheveux de Leonardo da Vinci."

"In 1925, an American collector bought this relic in Paris ... Later, before dying aged 95, he sold it on to another American collector, who contacted us," Alessandro Vezzosi, director of Italy's Ideale Leonardo da Vinci museum, told Reuters.

The hair is slated to make its first public appearance at a press conference this week before going on display at the museum to mark the 500th anniversary of da Vinci's death.

A portrait of Leonardo da Vinci Scholars suggest hair found in a private U.S. exhibit may belong to the Renaissance master. (Photo: Francesco Melzi/Wikipedia)

If proven authentic, the luminary's lock could crack an even more intriguing da Vinci code: As in, does anyone know where da Vinci is these days?

Towards the end of his life, the artist lived in Ambroise, France at the behest of King Francis I. Reportedly, the French monarch hoped to avail himself of da Vinci's engineering and artistic genius. Sadly, in his 60s, da Vinci was already in failing health, having suffered several strokes. He died in Ambroise in 1519, at the age of 67.

That's where the historical picture gets a little muddied. Scholars presume da Vinci was buried in the Chapel of Saint-Florentin at the Château d'Amboise — but the chapel was subsequently consumed by flames during the French revolution.

Pages from Leonardo da Vinci's notebook A page from the notebooks of Leonardo da Vinci showing a geared device disassembled. Circa 1500. (Photo: Everett Historical/Shutterstock)

Did his bones at least make it out of the fire? Prevailing opinion has it they were moved to another, smaller chapel nearby called Saint-Hubert. That's where the remains are said to rest today.

Except maybe not. Even a plaque at Saint-Hubert leaves the door open for bone-tingling intrigue by claiming it's only the "resumed" location of his body.

The DNA test on his supposed hair may finally remove that longstanding presumption.

Tomb of Leonardo da Vinci Leonard's presumed tomb in the chapel of Saint-Hubert. (Photo: Wikipedia)

2. He saw saw the world like few others did — literally.

Speaking of presumptions, we've traditionally revered da Vinci as a man who not only thought, but also saw, outside of the box — a man whose unerring visions allowed him to sketch technical diagrams in unerring detail as well as masterpieces like "The Last Supper" and the "Mona Lisa."

But what if that uncanny vision was actually the product of defective eyes? Da Vinci, a recent study suggests, may have suffered from a form of strabismus, commonly referred to as "crossed eyes."

"Looking at his work, I noticed the pronounced divergence of the eyes in all of his paintings," noted study author Christopher Tyler of London's City University.

Tyler pored over six of da Vinci's works — all of them either portraits of self portraits of the artist. By drawing circles on the pupils, irises and eyelids and measuring their positions, Tyler determined the gaze of each eye.

His conclusion? They aren't looking in exactly the same direction at the same time.

Da Vinci's crossed eyes may have actually offered him a unique vantage of the world, allowing him to render that reality with a fresh, often breathtaking perspective.

3. The painting behind The Painting...

It's probably fair to say more breaths have been taken away in the presence of da Vinci's "Mona Lisa" than any other work of art ever. Painted in 1503, it still glistens with mystery. Like, for instance, how she appears to be smiling and yet, when we look directly at her mouth, there a decidedly downward dip along the edges. Could the Mona Lisa smile actually be a Mona Lisa frown?

Mona Lisa Her enchanting smile might actually represent a later edit to an earlier portrait. (Photo: Leonardo da Vinci)

But the intrigue hardly ends there. In fact, that "smile" only gets more mystifying when we consider the portrait beneath the portrait. Back in 2004, French scientist Pascal Cotte was allowed to analyze the painting from its permanent perch at the Louvre. Using Layer Amplification Method — essentially bombarding the work with intense lights — he made a striking discovery: There's a painting of the same subject buried beneath the work.

And that subject, with its larger head and nose, but smaller lips, is certainly not smiling. But, more importantly, Cotte noted, it should finally lay to rest any debate over who da Vinci was painting.

"I am absolutely convinced that the Mona Lisa is Lisa," he said.

As in Lisa Gherardini, the wife of a silk merchant from Florence, and long the subject of scientific scrutiny. Did she really own the most famous face in art history?

She certainly did, Cotte said. And we now have the evolution of her portrait.

"I am absolutely convinced that the Mona Lisa is Lisa," he said.

4. His genius for sketching anatomy had a glaring limitation.

Da Vinci's file on human anatomy is as painstakingly detailed as it is voluminous. Even centuries later, they stand as medical masterpieces: the first accurate depiction of a human spine, the earliest known description of cirrhosis of the liver, a human fetus.

Photo of Da Vinci's 'Vitruvian Man' Photo of Da Vinci's 'Vitruvian Man' from 1492. (Photo: Janaka Dharmasena/Shutterstock)

He derived much of his insight into the human body from years spent dissecting corpses. (Yes, da Vinci had a "license to Frankenstein.")

But where his 240 or so diagrams fall painfully short is on the female side of the equation. Da Vinci couldn't offer much insight into the female body, particularly the reproductive system. That's because, while anatomists had access to human bodies for study, most of those bodies were of the unclaimed variety — drunks and vagrants — and not many of those happened to be women.

"It was definitely harder to get female bodies to dissect, and he didn't have many opportunities," Peter Abrahams of the University of Warwick Medical School told LiveScience.

And so the master's all-seeing eye crashed into a very practical wall. Not one to give up easily, da Vinci examined the corpses of female animals, hoping to extrapolate the results for humans.

It was, perhaps, the only time that Da Vinci's efforts fell so woefully short.

5. He was really into war machines.

A catapult model designed by Leonardo da Vinci The catapult was around long before da Vinci. But, of course, he saw room for improvement in its design. (Photo: Mar.K/Shutterstock)

If there's one area we should be grateful that da Vinci didn't quite master it would be his passion for war machines. He may have cast a light on the intricacies of the human interior. He may have vastly expanded our understanding of engineering and literature.

But he also also liked to design some pretty hair-raising mechanical monstrosities.

Take, for example, the aforementioned tank. It was basically a rolling bunker that could pivot in any direction with light cannons and other anti-personnel devices jutting out from beneath its tortoise-like shell.

The tank design went along with various concepts for human gliders, submarines and other works of fear and awe. The great humanitarian for the ages didn't seem to mind the occasional anti-humanitarian flourish.

Or did he? When modern-day engineers tested the soundness of da Vinci's tank design for a BBC documentary, they noted that it had one very obvious practical flaw. The gears were set against each other, essentially crippling the tank right out of the gate.

And his concept for a human glider?

"The way he suggested you operated it was the exact opposite of what you should actually do and would have resulted in the pilot plunging to earth," documentary producer Michael Mosley noted in the Telegraph. "But Leonardo studied birds and knew how their wings worked. It would have been aerodynamic madness to suggest what he did."

Da Vinci should have known better, right? Indeed, he likely did. And even at the height of his genius, he never lost sight of the humanity he so loved.

5 surprising facts about Leonardo da Vinci
500 years later, the world still celebrates Leonardo da Vinci, the ultimate Renaissance genius.