Metastability's a general scientific concept which describes states of delicate equilibrium. A system's in a metastable state when it's in equilibrium (not changing with time) but's susceptible to fall into lower-energy states with only slight interaction. It's analogous to being at the bottom of a small valley when there's a deeper valley close by - a local stability of a system at a local (but not global) minimum of a potential. Almost any system can demonstrate metastability, but it's most… (More on Metastable)