It's been forty years since Eero Aarnio created the Bubble Chair, a seat constructed of transparent acrylic that – in case the name doesn't give it away – you can see through.  For the past four decades, Aarnio and his Bubble pretty much cornered the transparent seating market.  But no more.  Today, modern furniture you can't see is everywhere.  It started with Kartell and their Philippe Starck - designed Ghost chairs, a partnership that has grown to produce transparent chairs, lamps, tables and accessories in several styles.  And it has grown into a phenomenon.