Scientists have made nano-flowers just 25 micrometers across -- that's less than 0.025 millimeters. A quarter of one per cent of a millimeter!
New Scientist magazine explains the scientists' process: "They made the bouquet in the false-colour image on the left in three stages. First, they chilled a solution of sodium silicate and barium chloride to 4 °C. At this temperature, more carbon dioxide from the air dissolves in the liquid, triggering a chemical reaction that lays down bundles of barium carbonate and silica (red).