This paper reviews some of the interesting applications of semiconductor nanocrystals embedded in glasses. Because of their unique electronic and optical properties, semiconductor quantum dots (QDs) found wide applications in photonics. They are inexpensive and robust material and have attracted a great attention in the application of 1.3-1.5 μm optical communication. Embedding semiconductor QDs in spherical microcavities is also an attractive system both for fundamental physics research in the field of cavity quantum electrodynamics and for its potential application in lasing materials. Energy transfer processes and coupling-strength between nanocrystals can be studied and demonstrated using semiconductor nanocrystals doped glasses. It has been established that an efficient energy transfer occurs between QDs having a significant band gap energy difference, i.e., between dots of markedly different sizes. We demonstrate that a promising way to enhance energy transfer between different subsets of QDs is to red-shift the emission sufficiently far from the host absorption so that self-absorption by the host becomes negligible.