The use of labeling or staining agents has greatly assisted the study of complex biological interactions in biology and the fluorescent labeling of biomolecules has been demonstrated as an indispensable tool in many biological studies. By virtue of excellent fluorescence properties the Silica nanobeads find application in biological labeling, bioimaging, biosensing etc. Ultrastable particles exhibit a very high resistance to photobleaching and can be used in single-particle imaging as well as in super resolution techniques such as stimulated emission depletion (STED) microscopy.