aRWIN (Data Research Warehouse Information Network) is an in-house solution developed by the Royal Belgian Institute of Natural Sciences (RBINS), as a Natural History collections management system for biological and geological samples in collections. In 2014, the Royal Museum for Central Africa (RMCA) adopted this system for its collections and started to take part in new developments. The DaRWIN database currently manages information on more than 600,000 records (about 4 million specimens) housed at the RBINS and more than 650,000 records (more than 1 million specimens) at the RMCA. DaRWIN is an open source system, consisting of a PostgreSQL database and a customizable web-interface based on the Symfony framework (https://symfony.com). DaRWIN is divided into 2 parts: one public section that gives a read-only access to digitised specimens, one section for registered users, with different levels of access rights (user, encoder, conservator and administrator), customizable for each collection and allowing update of specimens and collections, daily management of collections, and the potential for dealing with sensitive information. DaRWIN stores sample data and related information such as place and date of collection, missions and collectors, identifiers, technicians involved, taxonomy, identification information (type, stage, state, etc.), bibliography, related files, storage, etc. Other features that deal with day-to-day curation operations are available: loans, printing of labels for storage, statistics and reporting. DaRWIN features its own JSON (JavaScript Object Notation) webservice for specimens and scientific names and can export data in tab-delimited, Excel, PDF and GeoJSON formats. More recently, a procedure for importing batches of data has been developed, based on tab-delimited files, making integration of data from (old/historical) databases faster and more controlled. Additional improvements of the user interface and database model have been made. For example, parallel taxonomical hierarchies can be created, allowing users to work with temporary taxonomies, old scientific names (basionyms and synonyms) and document the history of type specimens. Finally, quality control and data cleaning on several tables have been implemented, e.g. mapping of locality names with vocabularies like Geonames, adding ISO 3166 two-letter country codes (https://www.iso.org/iso-3166-country-codes.html), cleaning duplicates from people/institutions and taxonomy catalogues. A tool for checking taxonomical names on GBIF (Global Biodiversity Information Facility), WoRMS (World Register of Marine Species) and DaRWIN itself, based on webservices and tab-delimited files, has been developed. Last year, RBINS, RMCA and Meise Botanic Garden (MBG) defined a new framework of collaboration in the NaturalHeritage project (http://www.naturalheritage.be), in order to foster interoperability among their collection data sources. This new framework presents itself as one common research portal for data on natural history collections (from DaRWIN and other existing collection databases) of the three partnered institutions and makes data compliant to a standard agreed by the partners. See Poster "NaturalHeritage: Bridging Belgian Natural History Collections" for more information. DaRWIN is accessible online (http://darwin.naturalsciences.be). A Github repository is also available (https://github.com/naturalsciences/natural_heritage_darwin).