they were part of ukraine after the soviet break, they wanted to break away from ukraine but ultimately stayed but with a lot of independence from the rest of ukraine. the thing is, this whole deal in ukraine with the protests, etc. doesn't revolve around just crimea, it's half of ukraine vs. the other half, with crimea just being the problem penisula it's always been (it has a rich history, the last opposition to the communist party taking over russia after ww1 was beaten/massacre'd in crimea).
the russians just moved into crimea because of their naval base, but i think ultimately half of ukraine will break off.