Two-dimensional (2D) atomic sheets yield collective properties of mechanical flexibility, electrical control, optical transparency and high surface-to-volume ratio, which hold promise for advanced flexible nanoelectronics and sensors. This work explores two newly emerging 2D materials, silicene and phosphorene (the Si and P equivalent to graphene) and their air-stability and device study. The debut of silicene transistor confirms ambipolar transport behavior in atomically thin Si with greater gate modulation than graphene, indicating potential device reach beyond graphene. On the other hand, phosphorene exhibits high mobility and tunable direct bandgap even on plastic substrates, making it the most suitable contemporary 2D semiconductor that combines the merits of graphene and transitional metal dichalcogenides. This recent progress on silicene and phosphorene represent a renewed opportunity for future nanoscale and flexible devices.