A long-standing problem in quantum information is: what are the resources that make quantum computers able to perform computational tasks in a way that outperforms any kind of classical Turing machine? The flip side of the same question is: what makes quantum mechanics so hard to simulate? These questions are at the core of the notion of quantum complexity. In this talk we will show that quantum advantage and quantum complexity arise from the conspiracy and interplay of two entropic resources, Entanglement Entropy and Stabilizer Entropy. In particular, quantum complex behavior arises when stabilizer entropy gets scrambled around, giving rise to Scrambling Entropy (SE). We will provide an introduction to the resource theory of SE and applications in quantum thermodynamics, quantum metrology, black-hole physics, and foundations of quantum mechanics.