We apply a high-resolution interference microscope with spectral resolution to investigate the scattering response of isolated meta-atoms in real space. The final meta-atoms consist of core-shell clusters that are fabricated using a bottom-up approach. The meta-atoms are investigated with an increasing complexity. We start by studying silica and gold spheres and conclude with the investigation of the meta-atom, which consists of a silica core sphere onto which gold nanospheres are attached. Numerical simulations entirely verify the measured data. The measuring process involves recording the intensity and phase of the total field emerging from the scattering process of an incident light at the particle in the transmitted half-space with spectral and high spatial resolution. We show that spectrally resolved high-resolution interference microscopy can be used to differentiate between nanoparticles and characterize single meta-atoms, something that is rarely accomplished.