Einstein’s theory of general relativity tells us that gravity comes from curved space-time geometry. The space-time is like a plastic membrane which we can stretch with our energy and momentum. But what is this membrane made of? What glues the spacetime together? These questions are not philosophical, but have to be understood in order to develop a complete theory of gravity. In particular, we need a more “microscopic” understanding of spacetime to know how quantum mechanics interplay with gravity. In recent years, progress in the field of holographic duality has shown that quantum entanglement plays a key role in “gluing” space-time together. The curved space-time geometry may emerge as an effective description of the entanglement structure in many-body quantum states. In this talk, I will describe a few toy models that illustrate this idea. I will discuss how a family of quantum states known as tensor network states naturally relate geometry and entanglement. As a more concrete dynamical model, I will discuss how to build a two-dimensional “eternal” traversable wormhole by gluing two copies of Sachdev-Ye-Kitaev (SYK) model.