Surface tension generally plays a negligible role on macroscopic scales, but it is often the dominant force on nanometer to micrometer length-scales. The efforts of this dissertation are mainly focused on understanding the role that surface tension plays on sub-millimeter scale objects, especially on soft material systems, and how to utilize this phenomenon to assemble and deform objects. This dissertation addresses several phenomena of nano-and micron-sized objects at fluid interfaces. For nano-scale objects, amphiphilic block copolymer chains were used to explore interfacial behaviors due to their enhanced stability, mechanical properties, and tunability compared to other interfacially active materials such as small molecule surfactants or lipids. We investigate the tailoring of amphiphilic block copolymer assemblies through deformation at the oil/water interface by inducing interfacial instabilities to incorporate inorganic nanoparticles into micelles (chapter 2) or by controlling osmotic stresses to prepare multi-compartment emulsions and capsules (chapter 3). Next, we utilize photo-crosslinkable and temperature-responsive copolymer networks (i.e., thin hydrogel sheets) with simple to complex geometries as micro-scale soft objects. Competition between surface energy and elastic bending energy allows us to quantitatively characterize elastic properties of crosslinked thin hydrogel sheets in micron dimensions by using surface tension of liquids (chapter 4). In addition, we have found significant edge imperfections due to the finite resolution of the photo-lithographic patterning method by observation of interfacial deformations. We employ the edge imperfections to drive the buckling of narrow photo-crosslinkable hydrogel ribbons (chapter 5). Lastly, we introduce a new concept of capillary assembly of soft hydrogel sheets with various geometries. This study allows us to examine correlations between elastic properties and surface tension, as well as capillary interactions between soft materials which can be extended to more complex multi-polar interface deformation (chapter 6).