HR diagram for the Class II YSOs of NGC 1333 (green stars), Lupus (orange crosses), and Cha I (purple asterisks). The green, orange, and purple lines correspond to the median of NGC 1333, Lupus, and Cha I samples (sub-luminous objects are not included), respectively. The birthline (Palla & Stahler 1993) is plotted as a dot-dashed line. Black solid and dashed lines show the isochrones and evolutionary tracks by Siess et al. (2000).