Quantum many-body problems still remain largely unsolved because their information content grows exponentially with particle number due to interactions. I will overview why identifying particle clusters yields a realistic first-principles description of diverse many-body and quantum-optics problems, and why it introduces the control of clusters – clustronics – as a powerful approach to realize macroscopic quantum effects. I will discuss how clustronics theory can realistically guide experiments by showing several examples involving semiconductors and atomic Bose-Einstein condensates.