Tracking the early traces of life preserved in very old rocks and reconstructing the major steps of its evolution is an exciting and most challenging domain of research. How amazing it is to have a cell that is 1.5 or 3.2 billion years old under a microscope! From these and other disseminated fragments of life preserved along the geological timescale, one can build the puzzle of biosphere evolution and rising biological complexity. The possibility that life may exist beyond Earth on other habitable planets lies yet at another scale of scientific debates and popular dreams. We have the chance now to live at a time when technology enable us to study in the finest details the very old record of life, or to land on planets with microscope and analytical tools, mimicking a geologist exploring extraterrestrial rocky outcrops to find traces of water and perhaps life. There is still a lot to be done however, to solve major questions of life evolution on Earth, and to look for unambiguous life traces, on Earth or beyond. The project ELiTE aims to provide key answers to some of these fundamental questions.Astrobiology studies the origin, evolution and distribution of life in the Universe, starting with life on Earth, the only biological planet known so far. The ambitious objectives of the project ELiTE are the following:1) The identification of Early traces of life and their preservation conditions, in Precambrian rocks of established age2) The characterization of their biological affinities, using innovative approaches comprising micro to nanoscale morphological, ultrastructural and chemical analyses of fossil and recent analog material3) The determination of the timing of major steps in evolution. In particular, the project ELiTE aims to decipher two major and inter-related steps in early life evolution and the rise of biological complexity: the evolution of cyanobacteria, responsible for Earth oxygenation and ancestor of the chloroplast, influencing drastically the evolution of life and the planet Earth, and the evolution of the domain Eucarya since LECA (Last Eucaryotic Universal Ancestor).4) The determination of causes of observed pattern of evolution in relation with the environmental context (oxygenation, impacts, glaciations, tectonics, nutrient availability in changing ocean chemistry) and biological innovations and interactions (ecosystems evolution).Objective 1 has implications for the search for unambiguous traces of life on Earth and beyond Earth. Objectives 2 to 4 have implications for the understanding of causes and patterns of biological evolution and rise of complexity in Earth life. Providing answers to these most fundamental questions will have major impact on our understanding of early life evolution, with implications for the search for life beyond Earth.