In the future, robots will be used to build a lot of things for us, including other robots. Researchers at MIT’s Center for Bits and Atoms already working on Assembler robots that could eventually build anything. Their system involves tiny subunits called voxels. As MIT explains:
The robots themselves consist of a string of several voxels joined end-to-end. These can grab another voxel using attachment points on one end, then move inchworm-like to the desired position, where the voxel can be attached to the growing structure and released there.
The below video shows how these robots work.