Lyophilization (or "Freeze Drying " by it's simpler name) is the process of removing 98% of the moisture from an item. It involves the item being frozen solid and under high vacuum (low air pressure) gradually warmed up to around 50 degrees Celsius.

This means that using this process with ice cream, the moisture content goes straight from ice to vapour, bypassing water, and is discarded leaving a dry crunchy and very edible treat.

As if by magic, when a freeze dried food is reconstituted (that is, when it's water content is added back) the colour, texture, taste, aroma, nutritional value, structure and weight are nearly identical to how is was before the freeze drying.

This technology isn't exactly new, however. Those clever guys in the later Inca civilizations were doing a form of freeze drying several hundreds years ago. They used the night and day temperature variations in the high altitudes of the Andes to enact the same effect with great success.

Commercial freeze drying using modern man's machinery was first introduced in the 50's and today we use freeze drying in a vast array of industries with many applications including using the freeze drying process to create the Australian army's MRE's (Meals Ready to Eat) for use in the field.