From transcriptomic landscapes to tissue function. The 3 diagrams depict 2-dimensional landscapes with single cells as points, where a pool of progenitors gives rise to 2 differentiated populations X and Y. (A) A classical approach to identify a specific bipotent progenitor population, an immunophenotypic gate drawn based on expression of a surface marker (green) sections through the landscape and yields a heterogeneous population of cells upon functional analysis. (B) Normal hematopoiesis; dynamic information about cellular fluxes (arrows) indicates directions of differentiation throughout the landscape and degree of self-renewal. (C) An example of how cell-flux analysis reveals mechanisms of a disease. In this case, the stem cell pool is exhausted (low self-renewal), compromising production of Y cells, whereas there is increased production of X cells because of acquired increased self-renewal of progenitors X.