This study describes the formulation and properties of active fluids that contain mixtures of microtubules, polymer solutions, microtubule motor proteins, and ATP. These fluids are isotropic materials that display spontaneous self-organized flow patterns, sometimes persisting over hours, that are a consequence of motor-driven microtubule sliding and polymer-induced microtubule bundling. The project, organized by Zvonimir Dogic’s lab, was a multi-institutional collaboration involving labs from UC Santa Barbara, Hampton Univ., Worcester Polytechnic Inst., Harvard, and Brandeis.