With exciting advances in the spectroscopic imaging of biological molecules and the onset of single-molecule detection, optical trapping offers a complementary, versatile, and powerful technique for manipulating a wide array of biologically relevant particles in solution. Optical trapping offers useful means for measuring forces in the piconewton range, for observing displacements with nanometer resolution, and for the controlled initiation of dynamic processes with precise start times. The ease with which optical trapping can be integrated with microscopy techniques will make it an invaluable addition to a biologist's toolbox.