Holographic optical trapping uses forces exerted by computer-generated holograms to organize microscopic materials into three-dimensional structures. Achieving and verifying accurate three-dimensional placement requires methods for assessing the accuracy of the projected traps' geometry, as well as methods for measuring trapped objects' three-dimensional positions. Volumetric imaging of the projected trapping pattern solves one problem. Holographic video microscopy addresses the other. The combination is exceptionally effective for organizing, inspecting and analyzing soft-matter systems.