This lecture covers the concept of gradient drift in plasma physics, focusing on the guiding center motion of particles in a magnetic field. The instructor explains the equations governing the drift motion and the decomposition of the magnetic field. Various cases are considered, and the process of solving for the particle motion is detailed, including neglecting certain terms for simplification. Averaging over gyroperiods is discussed, leading to the derivation of equations for particle guiding centers. The lecture concludes with an analysis of the magnetic field behavior under different conditions.