Keywords: mixing, mix-norm, optimal stirring, ergodicity Abstract: I will discuss several issues in analyzing kinematics of a purely advective mixing process: 1) Determine whether the scalar quantity, such as dye, introduced into the flow field is - asymptotically - in time thoroughly mixed. 2) Determine how good is the mixture at any finite time. 3) Provide methods for open-loop optimization or feedback control of the mixture. The concept of ergodic partition allows us to discuss 1) precisely, and I will discuss some new results that allow us to compute it effectively. Concerning 2), the problem of an effective norm for mixing has attracted a lot of work over the last decade. I will discuss one family of norms - the so called mix-norm that connects to negative Sobolev space norms - that allows us to pursue study of opimization and control, thus covering 3). I will also discuss the question of ergodicity of a system and how to measure it. This is a departure from the standard off-on definition of ergodicity providing a measure of how close to ergodicity a system is. In all of the above, ergodic theory plays a prominent role.