Do the dry rocks carved from the ground still retain any original traces of prehistoric creatures? From mammoth tracks to petrified dinosaur footprints, scientists are unraveling big mysteries.

Since ancient times, people have been accustomed to using hammers and chisels to carve rocks to search for traces of ancient life. Derived from the Latin word fossilis, which simply means "to be dug up", the term fossil today represents priceless treasures of science.

However, how can a creature as fragile as a dragonfly's wing transform into an object so solid that it requires an iron hammer to touch? Professor Steve Brusatte, paleontology expert at the University of Edinburgh and author of the book The Story of Birds, has opened up insight into what really exists inside million-year-old rocks.

According to professor Steve Brusatte, the fossilization process takes place in countless ways with the participation of many different minerals. The prerequisite is that the organism must be buried quickly under a layer of sand or mud to avoid natural decomposition and environmental destruction.

The minerals then gradually seep into the remains, a process that scientific studies have shown can begin in as little as two years. Over a long period of time, most bones, teeth or shells of organisms are transformed into stone when the original material is replaced by minerals.

Basically, the ingredients that make up the hundred-million-year-old dinosaur bone that we touch today are no longer the original material of that creature's body.

However, surprising exceptions exist. In rare conditions such as creatures being instantly trapped in tree sap that turns into amber, or suddenly buried under volcanic ash and locked in rock, a part of the original material is still preserved intact.

Modern science, with increasingly sophisticated tools, has extracted DNA samples dating back more than a million years from fossils of species such as mammoths, although DNA cannot survive as long as in dinosaur fossils.

More remarkably, even in ultra-old dinosaur fossils, researchers still extracted organic soft tissues and proteins at the microscopic level.

These microscopic discoveries are fueling a boom in molecular paleontology, attracting brilliant young minds from the fields of chemistry and biology. Professor Steve Brusatte likens dna to an accurate paternity test that helps determine an organism's position in the evolutionary family tree. Meanwhile, protein sequences reveal unprecedented biological secrets: from metabolic rate, growth rate to how prehistoric creatures actually operated life.

The appearance of each fossil block is also a unique story depending on the local environment. The chemical composition of the underground water source - whether it is pure water or rich in iron and magnesium - and the characteristics of the mud and sand where it is buried will directly determine whether the fossil is hard or flexible, dull or colorful.

Minerals seeped into tree trunks over thousands of years have turned petrified wood into magical geological works. Even in Australia, the underground water environment is so perfect that it turns fossils of dinosaurs and mammals into real opal gemstones, typically small animal jaw bones that sparkle like jewels.

The magic of fossils is most clearly shown in trace fossils, such as footprints on the ground. Normally, a human footprint in the sand will be immediately washed away by ocean waves.

For a dinosaur footprint to petrify, it needs to walk on mud or sand, be dried by enough sunlight for a few hours to set its hardness, and then be deposited by a new layer of mud and sand in a moderately mild storm that is not enough to erode.

The odds of these factors occurring together are extremely rare, maybe just one in a billion or one in a trillion of feet touching the ground.

Steve Brusatte's former student, researcher Paige diPolo, once concluded that each fossil is a miracle. After hundreds of millions of years and millions of individual dinosaurs striding on the earth, that astronomical probability eventually left humanity with priceless pieces. These are rare windows into the distant past that people need to cherish and preserve.