The ocean's mesopelagic zone, or twilight zone, hosts the world's largest natural animal migration known as diel vertical migration (DVM). Every night, trillions of organisms, including a massive biomass of zooplankton and copepods, rise from depths of up to 1,000m to feed on surface phytoplankton. This nightly movement, which resembles a global "Mexican wave," plays a vital role in the Earth's climate by transporting up to six gigatonnes of carbon annually from surface waters to the deep ocean. Experts like Jon Copley and Laura Hobbs highlight that this "living soup" is essential for nutrient cycling and food webs. However, this critical ecosystem faces significant threats from climate change and potential deep-sea fisheries, prompting the IUCN to call for a pause on mesopelagic fishing to protect the entire water column.