The scattering spectra for different nanoparticles. The particles were 50-nm-AUNP and a 1-μm dielectric sphere in water medium. The inset shows the measured scattering images for single vesicle, AuNP and vesicle containing AuNPs. The nanometer-size AuNP has a comparable scattering intensity with microspheres. However, the AuNP shows yellow color and the vesicle shows blue. When endocytosis of AuNPs happens, the AuNPs became orange with blue surroundings. The optical scattering images can be used to identify the uptake of AuNPs.