Experimental and theoretical studies have revealed that weakly and moderately unstable baroclinic systems can experience a rich variety of vacillating and chaotic behaviors. Results have shown that the connection between steady, periodic and chaotic behaviors, i.e. the transition to chaos, may depend sensitively on different aspects of the physical system. However mechanisms causing these vacillating and chaotic behaviors are still not perfectly understood. The aim of this paper is to present a review of the related salient studies and to list the crucial questions which still persist and which could motivate expanded laboratory and numerical experiments.