This paper summarizes research on a new emerging framework for learning to plan using the Markov decision process model (MDP). In this paradigm, two approaches to learning to plan have traditionally been studied: the indirect model-based approach infers the state transition matrix and reward function from samples, and then solves the Bellman equation to find the optimal (action) value function; the direct model-free approach, most notably Q-learning, estimates the action value function directly. This paper describes a new harmonic analysis framework for planning based on estimating a diffusion model that captures information flow on a graph (discrete state space) or a manifold (continuous state space) using the Laplace heat equation. Diffusion models are significantly easier to learn than transition models, and yet provide similar speedups in performance over model-free methods. Two methods for constructing novel plan representations from diffusion models are described: Fourier met...