The collection started, of all places, at a botanical congress in Vienna in 1904 — the Eleventh International Botanical Congress, where attendees from across Europe agreed that the world's microscopic fungi were vanishing into specimen jars and personal notebooks faster than anyone could catalogue them. Someone needed to keep them *alive*. The Centraalbureau voor Schimmelcultures — the Central Bureau of Fungal Cultures — was the answer. Established the same year, it became the world's first dedicated repository of living fungal strains. Over more than a century it grew into one of the largest collections of fungi and bacteria on the planet, an international reference standard used by mycologists, ecologists, geneticists, food technologists, and medical researchers chasing down everything from grain rusts to opportunistic human pathogens. When a Dutch laboratory needs to know what a strange mould actually is, the CBS collection often holds the answer in a tube.

In 1907, a 24-year-old botanist named Johanna Westerdijk was offered the directorship of the new collection. She accepted. She would hold the post for fifty-one years. In 1917, the University of Utrecht made her an extraordinary professor of plant pathology — the first woman ever granted such a chair in the Netherlands. She kept the directorship; she added the professorship; and she ran them both for the rest of her working life. Her students remembered her as relentless and curious and entirely without patience for bureaucratic timidity. She published widely on plant diseases, mentored generations of female scientists at a moment when Dutch academia was overwhelmingly male, and lived by a personal motto often inscribed in old photographs of her: *Voor een werker is werken een lust* — *for a worker, work is a pleasure*. She died in 1961, three years after she stepped down.

For decades after Westerdijk's death the institute carried on under its old initials — CBS — and the name *Centraalbureau voor Schimmelcultures*, which is correct and accurate and entirely failed to honour the woman who had built it. On 10 February 2017, exactly a century after her 1917 professorship, that was put right. The institute was renamed the Westerdijk Fungal Biodiversity Institute, and the date was no accident — it was a deliberate centenary, a public acknowledgement that Dutch science had taken too long to credit one of its founders. The CBS strain numbers continue: every fungal sample in the collection still bears its CBS identifier, because changing tens of thousands of catalogue entries would have been chaos. But the building above them now bears her name.

Eight research groups operate inside the institute, each angled at a different question. Applied and Industrial Mycology under Jos Houbraken studies the moulds that make and unmake our food and medicines. Pedro Crous's Evolutionary Phytopathology team chases the fungi that destroy crops. Ferry Hagen's Medical Mycology group tracks pathogens that infect human bodies. Teun Boekhout works on yeasts and basidiomycetes. There is a group for fungal physiology, another for fungal natural products — the molecules these organisms make that sometimes become antibiotics or anticancer drugs — and one for software and databases, because a collection this large is increasingly a digital problem too. The institute hosts MycoBank, the global registry of fungal names, and publishes journals with titles like *Studies in Mycology* and *Persoonia*. Most visitors will never see the freezers. But somewhere in the basements of Utrecht Science Park, a hundred thousand quiet organisms wait in cold storage — a library of life, kept alive on Westerdijk's promise.