Challenges in Mechanics of Time-Dependent Materials,Mechanics of Biological Systems and Materials, and Micro-and Nanomechanics,Volume 2 of theProceedings of the 2021 SEM Annual Conference & Exposition on Experimental and Applied Mechanics, the second volume of four from the Conference, brings together contributions to this important area of research and engineering.  The collection presents early findings and case studies on fundamental and applied aspects of Experimental Mechanics, including papers in the following general technical research areas:Characterization Across Length...