Methylene (CH2) is the simplest carbene. The carbon is covalently bonded to two hydrogen atoms and bears two nonbonded electrons whose spins may be antiparallel (singlet state) or parallel (triplet state). It is an intermediary in the production and destruction of interstellar organic molecules.
Interstellar methylene was detected at a wavelength of about 4 mm by Hollis et al. (1995).