The dynamics of hybrid systems with mode dynamics of different dimensions is
described. The first part gives some deterministic examples of such multi-mode multi-dimensional
$(M^3D)$ systems. The second part considers such models under sequential switching at random times.
More specifically, the backward Kolmogorov equation is derived, and Lie-algebraic methods are used
in the case where the modes are linear. For Poissonian switched equi-dimensional modes, the diffusion
limit and its implication in vibrational stability are studied. The motion of a pebble on an
elevator belt is given as an example.