Argentine tango dancing relies heavily on improvisation; although certain patterns of movement have been codified by instructors over the years as a device to instruct dancers, there is no "basic step." One of the few constants across all Argentine tango dance styles is that the follower will usually be led to alternate feet. Another is that the follower rarely has his or her weight on both feet at the same time. In many modern variations of Argentine Tango, particularly in Europe, teachers of Tango may establish a "basic step" in order to help students to learn and pick up the "feel" of the dance.