  Studying the structure of nucleons is not only important to understanding the
strong interactions of quarks and gluons, but also to improving the precision
of new-physics searches. Since a broad class of experiments, including the LHC
and dark-matter detection, require Standard-Model backgrounds with parton
distribution functions (PDFs) as inputs for disentangling SM contributions from
potential new physics. For a long time, lattice calculations of the PDFs (as
well as many hadron structures) has been limited to the first few moments. In
this talk, we present a first direct calculation of the Bjorken-x dependence of
the PDFs using Large-Momentum Effective Theory (LaMET). An exploratory study of
the antiquark/sea flavor asymmetry of these distributions will be discussed.
This breakthrough opens an exciting new frontier calculating more complicated
quantities, such as gluon structure and transverse-momentum dependence, which
will complement existing theoretical programs for the upcoming Electron-Ion
Collider (EIC) or Large Hadron-Electron Collider (LHeC).
