The Human Cell Atlas Project aims to define all human cell types based on molecular profiles and connect this information with classical cellular descriptions. This initiative seeks to create a comprehensive reference map of the molecular state of cells in healthy human tissues, enabling systematic study of physiological states, developmental trajectories, regulatory circuitry, and interactions of cells. It also provides a framework for understanding cellular dysregulation in human disease. The project is an international collaborative effort committed to open data, code, and community. The Human Cell Atlas is a concept that aims to provide a detailed map of all human cells, including their molecular profiles, locations, and abundances. It is more than just a catalog; it is a map that aims to show the relationships among its elements. The atlas should abstract key features, provide coordinates, and show relationships. A natural solution would be to describe each human cell by a defined set of molecular markers, such as the expression levels of human protein-coding genes. The atlas should also include additional coordinates or annotations to represent histological and anatomical information, temporal information, and disease status. Such information is essential for harmonizing results based on molecular profiles with rich knowledge about cell biology, histology, and function. The Human Cell Atlas Project is analogous to the Human Genome Project, both being ambitious efforts to create 'Periodic Tables' for biology that comprehensively enumerate the two key 'atomic' units that underlie human life (cells and genes). The project will require and motivate the development of new technologies, as well as new mathematical frameworks and computational approaches. The Human Cell Atlas aims to provide a detailed understanding of anatomy, development, physiology, pathology, intracellular regulation, and intercellular communication. It will also provide invaluable markers, signatures, and tools for basic research and clinical applications. The project will involve the development of new technologies and computational approaches to achieve its goals.The Human Cell Atlas Project aims to define all human cell types based on molecular profiles and connect this information with classical cellular descriptions. This initiative seeks to create a comprehensive reference map of the molecular state of cells in healthy human tissues, enabling systematic study of physiological states, developmental trajectories, regulatory circuitry, and interactions of cells. It also provides a framework for understanding cellular dysregulation in human disease. The project is an international collaborative effort committed to open data, code, and community. The Human Cell Atlas is a concept that aims to provide a detailed map of all human cells, including their molecular profiles, locations, and abundances. It is more than just a catalog; it is a map that aims to show the relationships among its elements. The atlas should abstract key features, provide coordinates, and show relationships. A natural solution would be to describe each human cell by a defined set of molecular markers, such as the expression levels of human protein-coding genes. The atlas should also include additional coordinates or annotations to represent histological and anatomical information, temporal information, and disease status. Such information is essential for harmonizing results based on molecular profiles with rich knowledge about cell biology, histology, and function. The Human Cell Atlas Project is analogous to the Human Genome Project, both being ambitious efforts to create 'Periodic Tables' for biology that comprehensively enumerate the two key 'atomic' units that underlie human life (cells and genes). The project will require and motivate the development of new technologies, as well as new mathematical frameworks and computational approaches. The Human Cell Atlas aims to provide a detailed understanding of anatomy, development, physiology, pathology, intracellular regulation, and intercellular communication. It will also provide invaluable markers, signatures, and tools for basic research and clinical applications. The project will involve the development of new technologies and computational approaches to achieve its goals.