The new generation of ground-based, large-aperture solar telescopes promises to significantly increase our capabilities to understand the many basic phenomena taking place in the Sun at all atmospheric layers and how they relate to each other. A (non-exhaustive) summary of the main scientific arguments to pursue these impressive technological goals is presented. We illustrate how imaging, polarimetry, and spectroscopy can benefit from the new telescopes and how several wavelength bands should be observed to study the atmospheric coupling from the upper convection zone all the way to the corona. The particular science case of sunspot penumbrae is barely discussed as a specific example.