Establishing a permanent human foothold beyond Earth means solving problems no one has faced before, and this episode of The Universe walks through the engineering involved. Scientists and mission planners lay out competing proposals for lunar and Martian bases, from underground shelters that block radiation to greenhouse modules designed to grow food in sealed atmospheres. Waste recycling gets serious attention here, since a colony millions of miles from resupply has to treat water, air, and organic matter as things to be reused rather than discarded. The film also takes up terraforming Mars, the long-range idea of thickening its atmosphere and warming its surface enough to support open agriculture and eventually unprotected human life, and treats it as a centuries-long project rather than a quick fix. Interviews and animated simulations move between near-term hardware already in development and the far more speculative planetary-scale interventions, keeping a clear line between what could be built soon and what remains theoretical.