Why can plants survive frost or even freezing?

Early in the morning when walking my dog I see frozen due drops and brine on the leaves of a lot of gr like wild plants near the ground. When you walk on them you can hear them crunch. The next day when the sun comes out you see that they are thriving and look oh so healthy. Why don't they go limp like when green leafy vegetables get frozen lin the fridge and then thaw out into a limpy mess.?