**5. Conclusions**

As described in the preceding sections, several recent advances in in vitro network design and microrheological measurement techniques have enabled key insights into the mechanics and mobility of cytoskeleton networks.

The engineered networks include actin and microtubule networks with welldefined, versatile crosslinking motifs; networks of actin bundles mediated by counterion crossbridges, and composite networks of sterically and chemically interacting actin filaments and microtubules. The protocols and design schemes for these networks are highly modular to facilitate introducing higher levels of complexity and expanding the phase space of molecular constituents and structures. The versatile fluorescence labeling and imaging methods described allow for robust characterization of network dynamics and structure, while the active microrheology studies described can characterize the linear and nonlinear mechanical properties of these networks at the molecular and cellular scales. Some of the key findings this body of work has revealed include: the existence of critical strain rates and concentrations for actin networks to exhibit nonlinear mechanics, the inhomogeneous nature of stress propagation throughout crosslinked actin networks, the important role that actin plays in suppressing the buckling of microtubules, and the elegant competition between mesh size and polymer stiffness that leads to emergent dynamics in actin-microtubule networks.

While many open questions remain, these presented advances open the door for a wide range of highly-controlled new experiments to explore the vast phase space of mechanical and structural properties of diverse cytoskeleton networks.

*Microscale Mechanics of Plug-and-Play In Vitro Cytoskeleton Networks DOI: http://dx.doi.org/10.5772/intechopen.84401*
