Since a lot of the answers that have been received well are about intricate and hyper-realistic art work, let me share something else that I have stumbled upon in the internet.
These are hyper-realistic 3-Dimensional layered resin paintings by artist Riusuke Fukahori. He paints layers over layers of clear resin and builds 3 Dimensional paintings. He specializes in painting goldfish and considers himself a goldfish expert rather than a resin painting expert. He paints his fish in common Japanese household containers. The transparent and translucent features are painted with an unbelievable delicate touch.