“…As single-cell technologies [ 47 , 48 , 49 , 50 , 51 , 52 , 53 ] progress, it will also be possible to assess the role of cell-to-cell heterogeneity in metabolic properties and drug interactions. Extending the analysis to more cancer cell lines and primary cultures derived from different cancer types (e.g., colon, gastric, lung, skin, ovarian), to heterotypic spheroids including different cell types [ 54 , 55 ]—exploring a broader interval of spheroid dimensions and/or incubation times—may provide an even more complex picture. Finally, 3D structures formed from patient-derived cells [ 33 , 34 , 35 ] will provide an appropriate platform for designing personalized (multi)drug therapies.…”