This book provides a self-contained and systematic introduction to classical electron theory and its quantization, non-relativistic quantum electrodynamics.The first half of the book covers the classical theory.It discusses the well-defined Abraham model of extended charges in interaction with the electromagnetic field, and gives a study of the effective dynamics of charges under the condition that, on the scale given by the size of the charge distribution, they are far apart and the applied potentials vary slowly.The second half covers the quantum theory, leading to a coherent presentation of non-relativistic quantum electrodynamics.Topics discussed include non-perturbative properties of the basic Hamiltonian, the structure of resonances, the relaxation to the ground state through emission of photons, the non-perturbative derivation of the g-factor of the electron and the stability of matter.First released in 2004, this title has been reissued as an Open Access publication on Cambridge Core.