Quantum curves are conceived in physics literature. They are linear differential or difference equations in one variable, and sometimes a mixture of them. These are Weyl quantization of spectral curves appearing in different contexts of mathematics, such as integrable systems, random matrix theory, and Hitchin moduli spaces. The mathematical interest is not in identifying what they are. It is more in the point that considering an ODE as a quantum curve tells us the rich stories behind the scene, such as those for the case of $\zeta(3)$. I'll survey a few recent developments in quantum curves.