However, water molecules aren't the only invisible substance hiding all around you. (mindbodygreen.com)
Scientists coated fabric with a nearly invisible substance that can supercharge winter clothing and cut down on household heating. (cnbc.com)
Dark matter — the mysterious, invisible substance reckoned to comprise 80 percent of the universe's matter — clumped here and there, gravitationally drawing regular matter toward it. (discovermagazine.com)