The existing empirical evidence for evolved changes and selective advantages in robustness reinforces the importance of microbial systems in the study of evolutionary biology. But later work examining the relationship between robustness and evolvability is perhaps even more relevant for elucidating how infectious diseases evolve. On the one hand, the ability for robustness to allow phenotypic constancy in the face of environmental and mutational perturbation provides obvious benefits, such as reliable cellular function, individual development, and offspring reproduction. However, rigidity in the face of change may pose problems; because natural selection acts on phenotypic variation, robustness that buffers this variation could impede evolution by natural selection. These conflicting necessities force organisms to strike a balance between robustness and evolvability, the capacity to adapt. By examining this balancing act, we may learn whether evolvability can itself evolve; i.e., whether natural selection can exert a second-degree effect on evolution. Below we briefly describe two recent experiments on the relationship between robustness and evolvability.