In this paper researchers have identified the mechanism that controls the genetic determination of progenitors adult cells versus larval cells.  Drosophila tracheal system consist of  a population of  adult trachea progenitor cells arises from differentiated cells of the larval main trachea that retain the ability to reenter the cell cycle and give rise to the multiple adult tracheal cell types. These progenitors are unique to the second tracheal metamere as homologous cells from other segments, express  fizzy-related (fzr), the  Drosophila homolog of CDH1 protein of the APC complex, and enter endocycle and do not contribute to adult trachea. Our work examined the mechanisms for their quiescence and show that they reenter the cell cycle by expression of string/cdc25 through ecdysone. Furthermore, researchers have found that preventing endocycle entry is both necessary and sufficient for these tracheal cells to exhibit markers of adult progenitors, thus modifying their genetic program. Finally, the study shows that Hox-mediated regulation of fzr expression is responsible for progenitor identity and thus specifies a group of differentiated cells with facultative stem cell features.