It is well known that in the absence of convexity optimal controls may not exist. Under some assumptions, the convexified problem may have solutions. The original problem can be convexified by either taking closed convex hull of the orientor field or by introducing measure valued controls called relaxed controls. The talk is presented in the following sequence: (2) System models and Motivation, (3) Control Problems, (4) Some Basic Notations and Definitions, (5) Existence of Solutions and Regularity Properties, (6) Formulation of control Problems, (7) Some Results on Existence of Optimal Controls, (8) Open Questions.