Cryptocoryne is a genus of aquatic plants, a member of the Araceae family of monocotyledonous flowering plants. It is naturally distributed in tropical regions, from India to New Guinea. Crypts have been introduced to United States where they are considered as invasive weeds.
Arum spirale was the first described species in 1779, and since then the genus was intensively researched. The scientific classification is rather complicated and it has been revisited many times. Cryptocoryne species have tendencies to hybridize spontaneously and that causes a headache for taxonomists and confusion among aquarists. The common name of this genus is “water trumpet” which comes from the resemblance of their inflorescence to trumpet. 
Natural habitats of Cryptocorynes are rivers and river banks, streams and overflown forest pools. They can grow fully submerged under water or immersed, but the change between the two can cause a phenomenon called Crypt melt.
Legenandra is a genus closely related to Cryptocoryne and even though they belong to the same family, they can be easily distinguished by the arrangement of their leaves in a bud.
Cryptocoryne as a genus is characterized by tremendous biodiversity. Some species reproduce sexually and some vegetatively, some are endangered and some are invasive. They can grow in a wide range of pH values, from plants like C. balansae found in alkaline waters to acid loving plants.
There are few things to be taken in consideration when planting cryptocorynes in an aquarium. It is important to choose plants that are easy to keep and grow since most of the species are cultivated by experts. Cryptocoryne wendtii is an adaptable and versatile plant, ideal for beginners. It requires neutral or slightly acidic pH and a temperature range from 20 to 33 °C.
It’s very crucial to choose an aquarium that is not too brightly lit and to make regular water changes. Too much light and water filled with nitrates encourages algae to grow on the surface of their leaves. 
Cryptocorynes are very sensitive to transplantation and rapid changes in the environment. Moving them to another tank with different conditions will make their leaves whiter and disintegrate. They grow very slow but steady and it will take up to 30 days for new leaves to be established. 
As mentioned above, Crypt melt is a phenomenon that occurs when planting new crypts in an aquarium. To minimize the negative effects, it’s better to plant them in already established aquariums. Nowadays, nurseries ship crypts without leaves (as rootstock). Planting the root base is necessary since floating in the tank unplanted will affect their well-being. Harvesting cryptocorine seeds takes a lot of effort and propagation is usually done via their rhizomes. Once planted, they require small amounts of fertilizer and frequent water changes. They don’t coexist well in the same tank with cichlids, silver dollars and plecos.
Some reports show that crypts are used in Bangladesh as medicine for treating skin conditions like dermatitis, scars, acne, sores, eczema and infections.