Published 15 August 2012 Recently, we theoretically demonstrate that utilization of silica nanobeads co-doped with Cy3 and Cy5 molecules instead of single dye molecules as fluorescent labels can enable optical resolutions far beyond the diffraction-limit. Here, we show that by combining the 4Pi microscopy and the novel fluorescent label, it is possible to completely suppress the sidelobes in 4Pi focal spot and significantly enhance the optical resolution in the axial direction.