Fiber lasers are attracting intense worldwide attention in recent years due to their high power, low cost, compact size and excellent robustness. CW and nanosecond fiber lasers have already captured a significant portion of the industrial laser-material processing market from Nd:YAG and CO2 lasers. Similarly, ultrafast fiber lasers, delivering picoseconds and femtosecond pulses, are intensely studied and used in scientific applications, particularly those that demand uninterrupted operation over long periods of time. This talk will begin with a brief review of the state of the art of fiber lasers and the physics underlying their operation, including a new mode-locking regime, soliton-similariton regime that we have discovered. This will be followed by an overview of applications we are currently pursuing: processing of biomedical materials, sub- cellular surgery, development of optical-atomic clocks, as well as niche applications to next-generation accelerators: use of lasers for ultra-precise synchronization and electron beam diagnostics.