It is demonstrated that the melting temperature of nanocrystals embedded in a matrix exhibit two asymptotic limits as the size of the nanocrystal reaches its smallest value. The lower limit of melting temperatures is related to the disappearance of size-dependent entropy of melting and is considered as the lowest glass transition temperature which is located between Kauzmann temperature and glass transition temperature. The upper limit of a nanocrystal embedded in a matrix is determined by the ratio between the bulk melting temperature of the embedded nanocrystal and that of the matrix. The predicted thermodynamic melting temperature range and the lowest glass transition temperature are supported by available experimental evidences.