486958 Arrokoth and Pluto as windows on the composition of the early solar nebula

The recent New Horizons' flybys of KBO 486958 Arrokoth (2014MU69) and originally of Pluto have given us an opportunity to explore worlds that are far away from the Sun and therefore still preserve to some degree their original composition. They can give us a view of the primordial solar nebula at their respective 'birthplaces'. Pluto is thought to have formed closer to the Sun and then to have migrated outward with Neptune, Arrokoth instead is believed to have accreted close to its current location. Pluto and Arrokoth, represent two data points in our knowledge of the early solar system nebula and can shed light on the composition, structure, and evolution of our as well as other planetary systems. We summarize the current knowledge of these two bodies with a view to understand their role in the early solar nebula.