In this paper, we report on the versatile self assembly of water-soluble thiol-capped CdTe quantum dots (QDs), nanoparticles (NPs), or nanocrystals induced by L-cysteine (L-Cys). Major efforts are focused on the control of the self-organization of QDs into nanosheets (NSs), for example, by altering the solution pH and the QD size. The as prepared nanosheets exhibit bright photoluminescence (PL) and retain the size quantized properties of initial CdTe QDs, since they are actually formed by a 2D network of assembled QDs. By optical techniques; TEM, EDX, powder XRD, etc, it is found that the unique L-Cys-induced external destabilization is responsible for the template-free self-organization process, with the further assistance of the specific NP-NP interactions. And the internal chemical stability of initial CdTe QDs also is proven for the first time to play. an important role. These results help to enhance the current understanding about the mechanism for the destabilization of colloidal NPs and their self-assembly behavior.