  By using the state-of-the-art microscopy and spectroscopy in
aberration-corrected scanning transmission electron microscopes, we determine
the atomic arrangements, occupancy, elemental distribution, and the electronic
structures of dislocation cores in the 10{\deg}tilted SrTiO3 bicrystal. We
identify that there are two different types of oxygen deficient dislocation
cores, i.e., the SrO plane terminated Sr0.82Ti0.85O3-x (Ti3.67+, 0.48<x<0.91)
and TiO2 plane terminated Sr0.63Ti0.90O3-y (Ti3.60+, 0.57<y<1). They have the
same Burgers vector of a[100] but different atomic arrangements and chemical
properties. Besides the oxygen vacancies, Sr vacancies and rocksalt-like
titanium oxide reconstruction are also identified in the dislocation core with
TiO2 plane termination. Our atomic-scale study reveals the true atomic
structures and chemistry of individual dislocation cores, providing useful
insights into understanding the properties of dislocations and grain
boundaries.
