We use two-dimensional (2D) and three-dimensional (3D) imaging techniques to characterize sister samples of an immature Vaca Muerta shale before and after maturation in a pyrolysis cell. We use a series of electron microscopy and X-ray techniques to determine the mineralogical and structural properties of each shale sample before and after maturation. We verify successful maturation of the sample using programmed pyrolysis as well as before and after 2D and 3D images to determine changes in mineralogy, the shale fabric, and the development of microcracks. We observe new crack development in organic matter-hosted regions and along grain boundaries, as well as substantial growth of pre-existing microcracks and defects. The sum of porosity plus organic matter is constant before and after pyrolysis at 35%, indicating that the majority of pore volume creation occurs at the expense of organic matter removal.