A unit cell is a subset (usually rectangular or square) of the Life plane which tiles over the plane and has multiple states (distinct patterns) which simulate a cellular automaton, possibly itself. A unit Life cell is a unit cell that simulates the Game of Life.
The first unit Life cell was constructed by David Bell in 1996 . It employs standard glider logic to determine whether or not a glider should be present. The two states differ by a single glider. In 2004, Jared Prince modified David Bell's unit Life cell to support two, and therefore multiple, layers of Life universes, coined as "Deepcell"  .
More recently, a unit cell was constructed that simulates any Life-like cellular automaton .
Unit Life cell at the Life Lexicon.