Dragonfly life cycle in short. Eggs are laid in water or on vegetation near water, and hatch to produce pro-nymphs which live off the nutrients that were in the egg. They then develop into instars with approximately 9-14 molts that are voracious predators on other aquatic organisms, including small fishes. After some time (varies from a few months to several years, depending on the species), the nymphs crawl out of the water for their last molt, usually in dusk or dawn, into the flying teneral immature adults. The photo above is a snapshot of that process. Here the wings are still tiny and flabby. Within an hour or so they are pumped up and gradually become transparent and stiff. These insects soon transform into reproductive adults.
By the way, this is a Scarce Chaser (Libellula fulva/Bruine Korenbout).