Evidence continues to accumulate showing that tumors contain a minority 
population of cells responsible for tumor initiation, growth, and recurrence. 
These are termed "cancer stem cells" (CSCs). Functional assays have identified 
the self-renewal and tumor-initiation capabilities of CSCs. Moreover, recent 
studies have revealed that these CSCs is responsible for chemotherapy resistance 
within a tumor. Several mechanisms of chemoresistance have been proposed, 
including increased Wnt/β-catenin and Notch signaling, as well as high 
expression levels of adenosine triphosphate-binding cassette transporters, an 
active DNA repair capacity, and slow rate of self-renewal. Nanoscale 
drug-delivery systems, which transport therapeutically active molecules, prolong 
circulation, and improve biodistribution in the body, may allow more effective 
and specific therapies to address the challenges posed by CSCs. In particular, 
some nanovehicles are being exploited for selective drug delivery to CSCs and 
show promising results. In this review, we highlight the mechanisms of drug 
resistance and the novel strategies using nanoscale drugs to eliminate CSCs.