The proton has been a laboratory for carrying out precision tests of fundamental laws of nature and the search for new physics. In collider experiments, the spin and transverse structures of quarks and gluons inspire novel types of observables that probe the formation of the proton from its fundamental constituents. These structures are quantified by certain parton distribution functions (PDFs) that are not well determined by either theory or experiment so far. The PDFs have been extremely difficult to calculate from first-principle methods, particularly from lattice theory which simulates quantum gauge theories with supercomputers. In this talk, I will discuss a recent breakthrough in extracting the PDFs from lattice calculations, which is called large-momentum effective theory (LaMET). Through the rapid progress we made in the past few years, the lattice results of PDFs from LaMET have reached remarkable precision. Following this path, lattice theory can provide a complete tomography of the proton, which compliments next-generation experiments such as the electron-ion collider.