Explore graphs, trees, and disease spread modeling in this 28-minute lecture from MIT's 18.S191 Fall 2020 course. Learn about graph theory fundamentals, tree creation and traversal techniques, depth-first and breadth-first search algorithms, and their implementation using stacks and queues. Discover how these concepts apply to the SIR (Susceptible, Infected, Recovered) model for epidemic spread. Engage with interactive simulations and gain insights into plotting trees and using LightGraphs in Julia. The lecture covers various topics, including recursive schemes, infection spreading classes, and practical scripting examples. Participate in community efforts to improve video accessibility by adding timestamps and captions.