In a recent study published in Science Advances, materials scientists Julie A. Jackson and colleagues presented a new class of materials architecture called field-responsive mechanical metamaterials (FRMM). The FRMMs exhibit dynamic control and on-the-fly tunability for designing and selecting the construct's composition and structure. Typically, properties of mechanical metamaterials are programmed and set when the architecture is designed and constructed, without changing in response to shifting external environmental conditions or applications thereafter. The diverse characteristics of FRMMs were first demonstrated by printing complex structures of polymeric tubes filled in with magnetorheological (MR) fluid suspensions to allow remote magnetic fields to control the materials. Accordingly, the scientists observed rapid, reversible and sizable changes of the effective stiffness in the new metamaterial constructs.