Molecular bottlebrushes are building blocks for the design of unique polymeric materials whose physical properties are fundamentally governed by their densely grafted structures. Recent developments in the area of reversible deactivation radical polymerization enabled facile and effective control over multiple molecular parameters. Owing to large molecular size, anisotropic conformation, and reduced chain entanglement, molecular bottlebrushes have empowered various applications that are challenging to achieve with linear polymers. In this Review, we focus on determining correlations between brushlike architectures and materials properties.