What are the key reactions driving the global carbon cycle in Earth, the only known habitable planet in the solar system? And how do chemical reactions govern the transformation and movement of carbon? The special collection “Earth in five reactions - A deep carbon perspective” features review articles synthesizing knowledge and findings on the role of carbon- related reactions in Earth's dynamics and evolution. These integrative studies identify gaps in our current understanding and establish new frontiers to motivate and guide future research in deep carbon science. The collection also includes original experimental and theoretical investigations of carbon-bearing phases and the impact of chemical and polymorphic reactions on Earth's deep carbon cycle.