Closer than most people would ever dream to get. Francesca and her colleagues are inspecting Michelangelo's Sistin Chapel as part of a yearly maintenance work.

We have here some alterations, some light whitening. Now we need to understand what caused it.

The Sistin Chapel is part of one of the most visited museums in the world, with up to 25,000 tourists a day. But that comes at price.

The humidity increase and also the carbon dioxide. And this react with the surface of the work of art. We may have condensation dust deposit because dust means dangerous compounds.

After the last restoration 30 years ago, sensors and an air conditioning system were installed to keep a stable environment in the chapel. But since then, the number of visitors has soared, requiring more intensive maintenance.

With visitors gone, the Sistine Chapel really comes alive. You can see scenes like this, a team of scientists getting up there very close to Michelangelo's fresco to check for any sign of damage.

Behind the doors of the museum's lab, there's a small team of experts who look after its priceless collection. Fabio likens his job to that of a diagnostician who identifies the patient's symptoms and the main criticalities ahead of surgery. Here, he and his team are scanning a panel with an X-ray machine before the painting goes into restoration. But their main job in the past few weeks has been to get under the skin of Michelangelo's fresco. It shows us a fragment taken from a piece of cloth that was painted on a character after Michelangelo's death to cover its nudity.

To monitor a work of art, it is essential to know the materials it's made of. Here you can see Michelangelo's original plaster, the original color of the skin, and on top of it, in a lighter shade of pink with some black particles, is the clothes that was painted over.

As part of their work in the chapel, they are mapping sections of the sidewall frescoes using high-resolution images.

To get these details, we took 20 separate photos, and then we pieced them back together to obtain this extremely high-resolution image.

At such high resolution, we can see down to the single-pane crystal, and this allows us to see over time if there were changes or any dust deposits.

It's a comprehensive checkup, with experts even monitoring the calibration of the LED lights that were installed in the chapel.

The The old lights were unbalanced, so some of the colors didn't look their best. Instead, here you can see, the blue is well represented, as well as the green, the yellow, and the red. It's all very well balanced.

This year's maintenance has an added sense of urgency. The Vatican's Jubilee is starting in December, and even more visitors are expected here.

It's an important mission to be an open house, trying to balance, of course, the welcoming with the preservation of our incredible collections.

It's a fine line to ensure that present and future generations will still be able to gasp in all every time they look up a Michelangelo's masterpiece. Sara Monette, BBC News, Vatican City.