Cells differentiate through a series of changes in their potential to produce different cell types. Early embryonic cells are totipotent and can differentiate into any cell type, but this is usually lost after the eight-cell stage. Cells then become pluripotent stem cells or multipotent progenitor cells with more limited potential before terminally differentiating into mature cell types that cannot divide or take on other fates. The position of a cell, signaling chemicals, and its lineage influence which genes are expressed or silenced during differentiation.