Spherification is a molecular gastronomy technique involving sodium alginate (a gel-like substance extracted from brown seaweeds) and calcium ions from calcium lactate. Combining sodium alginate and calcium lactate produces calcium alginate. Calcium alginate is formed when the calcium ions from the calcium lactate knock the sodium ions from the sodium alginate. The resulting calcium alginate is a water-insoluble compound.
The calcium alginate compound can be used to encapsulate liquids, as it is water-insoluble. The encapsulated liquid is usually molded into a sphere, giving this technique its name.