Here's a breakdown:

* Limestone: This sedimentary rock is primarily composed of calcium carbonate (CaCO3), often formed from the accumulation of marine organisms' shells and skeletons.

* Metamorphism: This process involves intense heat and pressure deep within the Earth's crust. These conditions transform the existing minerals and structure of the rock.

* Marble: Under the influence of heat and pressure, the calcium carbonate crystals in limestone recrystallize and align, forming the characteristic interlocking texture of marble. This process also leads to the development of new minerals and sometimes distinctive patterns within the rock.

Essentially, marble is limestone that has been "cooked" by the Earth's heat and pressure, resulting in a new rock type with different properties and appearance.