This chapter is devoted to the topological invariants of analytic and algebraic functions and sets. We begin with description of the homology groups of nonsingular levels of germs of holomorphic functions with isolated singularity (the Milnor theorem) and with introduction of the Milnor bundle over a punctured disc. The action of the generator of the fundamental group of the base on a fiber defines the monodromy operator in the homologies of the fiber. Its action is described by the Picard–Lefschetz formula.