Biomining, the exploitation of microorganisms to extract metals of value from ores and mineral concentrates, was first commercially employed in the 1950s to leach copper from very large tonnages of submarginal-grade copper sulfide minerals in a process known as dump bioleaching. While this process application remains important, technology advancements led to engineered heap processes and continuous stirred-tank reactors using a variety of microorganisms. Today biomining is extensively used throughout the world for extracting base metals and enhancing gold recovery. Biomining commercial practices are described and illustrated and technical challenges are explained.