Stromule

A stromule is a microscopic structure found in plant cells. Stromules (stroma-filled tubules) are highly dynamic structures extending from the surface of all plastids, including chloroplasts. 
Protrusions from and interconnections between plastids were seen in 1888 and 1908, and have been described from time to time in the literature since then. 
Stromules were recently rediscovered in 1997. They exist in a number of angiosperm species including "Arabidopsis thaliana", wheat, rice and tomato, but their role is not yet fully understood.