Lightweight structures are the product of the science of making things as light as possible with constraints, which is conventionally referred to light yet sufficiently strong or stiff. The recent advancements in microfabrication have allowed the manufacture of structures with unprecedented properties. In this work, three strategies of achieving lightweight structures are explored: (1) hollowing, (2) folding, and (3) lightweight composites. The first strategy is demonstrated by creating a hollow flexural atomic force microscopy (AFM) cantilever. The hollow cantilevers are made by conformally depositing a thin layer of alumina on a solid beam and hollowing out the internal mold, resulting in the same overall dimensions with nanoscale wall thickness. Due to their significantly reduced weight, these hollow cantilevers exhibit low quality factors and comparable resonant frequencies to the solid cantilever, resulting in increased bandwidth and, correspondingly, capabilities for high imaging rate. In the second strategy, a self-deployable silicon-based propeller for microflyer is made with lightweight polymeric film. The propeller can be initially folded and then deployed by the apparent centrifugal force from rotation. The propeller exhibits lightweight yet sufficient thrust for flight which is promising for application in micro-aerial vehicles (MAVs) with potential to integrate MEMS sensors. Lastly, the last strategy is currently being explored by making thin composites. Thin composites can be made with a sandwich plate structure of materials with microscale thicknesses. Materials like carbon fiber and Mylar provides lightweight potentials that can be mechanical enhanced when reinforced by supplementary materials such as aluminum or alumina. These developments demonstrate the use of microfabrication to create lightweight structures with unique functionalities.