Present in all kingdoms of life, ABC (ATP-binding cassette) transporters form a large superfamily of integral membrane proteins. These proteins harness the energy of ATP binding and hydrolysis to translocate a multitude of chemically diverse substrates across cellular membranes. ABC transporters carry out their functions by undergoing cycles of large-scale conformational transition. Despite decades of studies and many available structures, the molecular mechanisms of most ABC transporters are still poorly defined. The ongoing revolution of cryo-EM has provided a unique opportunity for obtaining deep insights into these highly dynamic and versatile membrane protein machines. Through our cryo-EM studies of several ABC transporters that perform distinct functions, we have uncovered how distinct tasks of substrate translocation are accomplished by the unique actions of these transporters. Collectively, our findings demonstrate that ABC transporters have evolved to be highly efficient in ATP usage and work seamlessly with their designated substrates.