Nearly all lifeforms seen in BIONICLE are biomechanical, with a few exceptions like Krana and Kraata being completely organic, while Bohrok are fully mechanical (while Bohrok seem to be grown, other machine beings are artificially made and not considered lifeforms). Organic parts of creatures are very similar to real-world biological systems; for instance, Matoran are known to have lungs and muscles like humans do. The mechanical halves tend to include things like armor, hydraulic cylinders, gears, etc. built into their forms, and Matoran also have glowing "heartlights" on their chests; these mechanical parts are not electronic like computers in the real world, but are rather clockwork mechanisms with gears, pistons, etc.