For a long time, biologists have wanted to observe the inner workings of a cell as it divides. This challenge has now been addressed with advanced tools like fluorescence microscopy and super-resolution imaging, which allow scientists to see inside cells, track moving mitochondria, and watch them merge or split. Catherine Jessus, a biologist and research director at CNRS, explains that new imaging and genome sequencing techniques have made it possible to analyze and manipulate DNA, cells, and tissues at levels once thought impossible. These breakthroughs have opened up new fields of study, allowing scientists to explore life at the level of genes, populations, and entire ecosystems. Philippe Grandcolas, an ecologist and research director at CNRS, adds that understanding how organisms function—down to their genes and cells—requires considering their environment and the ecological interactions shaped by evolution. The concept of life has become more intricate as scientists discover systems that blur traditional definitions. Viruses, which were once excluded from the living world because they can't reproduce outside a host cell, have sparked debate after the discovery of "giant viruses" in 2003, which exhibit some life-like traits. Similarly, extremophiles—microorganisms that thrive in extreme environments such as geysers, deep-sea vents, and hyperacidic waters—have expanded our understanding of life’s potential. Many of these extremophiles are archaea, a group of microorganisms discovered in the 1970s and 1980s that revolutionized our view of life. Unlike bacteria and eukaryotes, archaea have unique cell membranes and lack a nucleus. Studying extremophiles presents significant technical challenges. Collecting them from extreme environments and growing them in laboratories is often difficult. Some may rupture when brought to the surface due to pressure differences, and others reproduce so slowly that obtaining enough samples is impractical. The Tara expedition, which explored oceanic plankton, revealed a vast diversity of microorganisms, with over 60% of Earth’s bacteria living in the oceans—yet less than 5% are known. This lack of knowledge is concerning, as many of these microbes play crucial roles in regulating the carbon cycle. Philippe Grandcolas points out that only about 10% of all living species are known, and every ecological field study tends to uncover new, previously unknown species—often small, unremarkable organisms like insects, worms, and microbes. The term "species" remains central to biology but is also ambiguous. While naming a species helps in understanding and discussion, it can sometimes create rigid definitions that fail to capture the complexity of life. For example, the traditional definition of species based on the ability to reproduce with others has been challenged by cases like wolves and dogs, which can interbreed, yet the ability of a chihuahua and a saint bernard to produce offspring complicates the idea of distinct species. The concept of clinal variation, where traits gradually change across a geographic area, further blurs species boundaries. Life is a complex web of interdependent organisms, each influencing and adapting to one another within larger ecosystems. Biodiversity is the result of both competition and cooperation, shaping the balance of life on Earth. Ecologists study these complex systems using mathematical models, artificial mini-ecosystems, and observations of key indicator species to understand ecosystem dynamics without knowing every component. However, they face urgent challenges, including cultural, political, and budgetary constraints that hinder ecological research. Philippe Grandcolas warns that simplistic views of biodiversity—treating species as fixed, unchanging entities—ignore the reality that they are dynamic lineages of individuals. He also criticizes the tendency of some decision-makers to believe that replacing lost ecosystems with artificial setups can provide the same ecological benefits, a belief that may not hold true. The ecological crisis is seen as a problem that can be modeled and addressed by mitigating climate change rather than relying solely on adaptation. However, Grandcolas is concerned about the rise of political and media figures who spread misinformation or deny scientific consensus. Budget cuts are imposing a "double brake" on research, limiting the future of ecological studies. Scientists working with wildlife, such as those tracking wolf populations, face harassment and accusations of misrepresentation. Decisions to "regulate" wolf numbers are seen as ecologically harmful, worsening the situation. Cuts to organizations like CNRS and the Ademe (Agency for Ecological Transition) are viewed as detrimental, creating a growing disconnect between society and the scientific community. The urgency to preserve biodiversity is pressing, as many species remain undiscovered, and the loss of life could lead to severe consequences, such as soil degradation, disrupted water cycles, and the emergence of new diseases. Ethically, the extinction of species is seen as unacceptable, with cascading effects that could profoundly impact the planet.