JOY PAN/GettyWhen most people imagine scientists discovering new species, they probably still picture an expedition into the unknown. A naturalist travels somewhere remote, perhaps on a wooden ship, and traipses through the jungle to encounter an animal or plant never before described by science. The intrepid explorer brings back specimens or observations to a museum, where they can be compared, named and described.There is some truth to this stereotype. Between 1854 and 1862, scientist Alfred Russel Wallace travelled through the Malay Archipelago, discovering animals and insects unknown to Western science. This led him to the theory of evolution by natural selection, contemporaneously with Charles Darwin.Antarctica had its own era of discovery. In 1840, scientists on a French expedition encountered what we now know as Adélie penguins. Imagine seeing penguins for the first time: strange black-and-white birds waddling over the ice, sliding on their bellies, leaping from freezing seas. Of course, “discovery” is a loaded word. Many animals and plants described by Western science were already known to Indigenous peoples and local communities. What changed was their entry into the formal scientific naming system – the global process by which species are compared, classified and recognised.Today, scientists are still finding new life in remote places and hidden inside the DNA of animals we thought we already knew.We still explore unknown worldsScientists still discover species this way: by probing Earth’s nooks and crannies and travelling to remote places to study what lives there. Last year, I was onboard the scientific vessel R/V Falkor (too) in Antarctica’s Weddell Sea, where one scientific team was searching for seafloor methane seeps. These are not just geological curiosities. Methane seeps create unusual habitats that harbour strange communities of life fuelled not by sunlight, but by chemicals rising from below. Scientists have already found new microbial diversity at Antarctica’s first known active methane seep. Not all hard-to-reach worlds are underwater. In Papua New Guinea’s Southern Fold Mountains, camera traps captured a shy, ground-dwelling bird slipping through rugged limestone forest. Scientists described it as a new species in 2025, the hooded jewel-babbler.But there is another kind of discovery happening too. White microbial mats underwater are telltale signs of seeping methane. Andrew Thurber, CC BY-ND Hidden species in familiar animalsSome species are not hidden because they live at the bottom of the sea or deep in a mountain forest. They are hiding in plain sight.Gentoo penguins are a good example. With their bright orange bills and comic waddle, they are familiar to anyone who has visited Antarctica. To most observers, they are simply “gentoos”.But our new research shows gentoo penguins are not one widespread species, but four. Our 2020 study first showed major genetic and physical differences between gentoo penguins from different islands. Now, using whole genomes – the complete set of genetic instructions inside an animal – and ecological modelling, we found these penguins are not just separated by distance, but have adapted to different Southern Ocean worlds. Gentoo penguins on Cuverville Island, Antarctica. David Stanley/flickr, CC BY-ND Learning to see in higher resolutionDiscoveries like this are often called “hidden” species. They look very similar to their relatives, but if we study their DNA, body measurements, behaviour and ecology, it’s clear they are separate species.Species discovery has always depended on the tools available. Early naturalists relied on what they could collect: feathers, skins, eggs and bones. These museum collections are like time machines and remain incredibly important. Today, whole genomes tell us if animals have different coding. Ecological models show whether animals live in different environmental conditions. Mathematical approaches test whether groups are evolving independently.In other words, we are learning to see biodiversity in higher resolution.This sharper view is changing how we understand familiar animals. For a long time, giraffes were considered one species, but genetics suggests they are four. My own work on forest birds in Madagascar found a new species of Newtonia bird.The Tapanuli orangutan is a powerful example. This Indonesian great ape from Sumatra was described as a new species in 2017, based on genomic, anatomical and behavioural evidence. It was extraordinary to recognise a new great ape in the 21st century, and sobering to realise fewer than 800 may remain.Again and again, the message is the same. The natural world is more complex than we know. And sometimes, by the time we recognise that complexity, a species may already be in deep trouble. The Tapanuli orangutan is a species of orangutan restricted to South Tapanuli in the island of Sumatra in Indonesia. It is one of three known living species of orangutan. Prayugo Utomo/Creative Commons, CC BY Why names matterTaxonomy – the science of naming and classifying life – can sound like an old-fashioned labelling exercise. But it’s how we map life on Earth.Conservation laws, threatened species lists and monitoring programs usually work at the species level. If several species are mistakenly treated as one, a declining species can be hidden inside a larger group that looks secure.As we stand at the precipice of Earth’s sixth mass extinction, this has never been more important.Recognising hidden biodiversity does not solve conservation problems by itself. But it helps us ask better questions. Which species are increasing? Which are declining? Which have not been counted for decades? These questions are urgent, because we are racing to understand biodiversity while climate change and habitat loss reshape life on Earth.Even now, in an age of satellites and genome sequencing, Earth still has secrets. Not only in the most remote places, but in the first animals we learn to recognise as children: penguins, giraffes, orangutans.The closer we look, the more life reveals itself. Our task now is to keep looking and protect the richness that was there all along.Jane Younger receives funding from the Australian Research Council, National Geographic Society, Rolex, WIRES, the Marine Megafauna Research Fund, and Lindblad-National Geographic. She is affiliated with the University of Tasmania and Senior Editor of Ecology & Evolution.