  The aversion of hydrophobic solutes for water drives diverse interactions and
assemblies across materials science, biology and beyond. % Here, we review the
theoretical, computational and experimental developments which underpin a
contemporary understanding of hydrophobic effects. % We discuss how an
understanding of density fluctuations in bulk water can shed light on the
fundamental differences in the hydration of molecular and macroscopic solutes;
these differences, in turn, explain why hydrophobic interactions become
stronger upon increasing temperature. We also illustrate the sensitive
dependence of surface hydrophobicity on the chemical and topographical patterns
the surface displays, which makes the use approximate approaches for estimating
hydrophobicity particularly challenging. Importantly, the hydrophobicity of
complex surfaces, such as those of proteins, which display nanoscale
heterogeneity, can nevertheless be characterized using interfacial water
density fluctuations; such a characterization also informs protein regions that
mediate their interactions. Finally, we build upon an understanding of
hydrophobic hydration and the ability to characterize hydrophobicity to inform
the context-dependent thermodynamic forces that drive hydrophobic interactions
and the desolvation barriers that impede them.
