This chapter explores the origins of the planetary boundaries, which comes from the recognition that we’ve entered the Anthropocene and that the exponential pressures on the Earth system are leading us towards catastrophic, irreversible tipping points in the Earth system. The planet can exist in multiple separate states separated by a threshold, the ideal state being the Holocene. For each of the environmental processes, we must recognize and maintain a quantitative science-based boundary -- beyond which we risk feedbacks, interactions, and surprise that could push the system out of the Holocene. The planetary boundaries framework rests on three pillars of scientific enquiry: understanding the Earth as a self-regulating biogeophysical system, understanding the relationships between human needs and the capacities of our biosphere to support humanity, and enormous advancements in understanding resilience theory and complex systems research. "Limits to growth" is a famous theory from the 1970s, similar to carrying capacity; the planetary boundary framework differs by decoupling itself from the needs of humanity.