In recent decades, the Arabidopsis root system has been extensively used to dissect developmental processes because of its simplicity and the predictability of cell fate. Its root meristem is composed of concentric layers of epidermis, cortex, and endodermis encircling the stele that contains the vascular system. Each cell file can be traced to the initials and a mitotically less-active quiescent center (QC), which serves as the stem cell niche. The combination of PLETHORA, SCARECROW, and SHORT-ROOT transcription factors, as well as local auxin distribution, are essential for correct positioning of the QC and maintenance of that niche. In the epidermis, fates for the root hair-bearing (H) and non-hair (N) cells are determined by their positions relative to neighboring cells. Recent molecular genetics studies have provided insights into the molecular mechanisms for this specification of position-dependent cell fate and regulatory circuits in the Arabidopsis epidermis. Taken together, such positional information plays a key role in dictating the stem cell niche and cell fates.