**Abstract: **String theory is the only known mathematically consistent theory of quantum gravity, but it is infamously difficult to test experimentally. In this talk, we will discuss recent progress in bridging the gap between string theory and the real world, showing how a simple, well-supported statement inspired by string theory called the Weak Gravity Conjecture places strong constraints on certain models of cosmological inflation. This example is part of a larger program of quantum gravity research, which has led in recent years to important new insights in cosmology, particle physics, quantum field theory, pure mathematics, and the relationships between them.