This Dutch video says about itself (translated):
April 15, 2016
In the east of the Netherlands last year was discovered a small population of pygmy damselflies (Nehalennia speciosa), an extremely rare damselfly species, reports Nature Today. The last times the pygmy damselfly has been found in our country were 1912 and 1955. The species has greatly deteriorated in all of Western Europe by damage to nature and the environment.
This is the smallest damselfly species of Europe. The video shows them mating.