Visited by Gottfried Leibniz

November 18, 1676

On his way back to Germany from England, Leibniz spent a few days in the Dutch Republic. While in England, he had spent time with Henry Oldenburg, who no doubt told him about Leeuwenhoek's recent observations of little animals in infusions. While in the Republic, Leibniz met both Leeuwenhoek in Delft and Spinoza in nearby Voorburg, a village between Delft and Den Haag.

Leeuwenhoek may well have showed Leibniz the little animals in some of the infusions about which he had written to the Royal Society six weeks earlier, in October. At the end of Leeuwenhoek's letter of 9 October reporting on the little animals, Oldenburg wrote a note suggesting that he had entrusted his reply of 16 October (O.S.) with Leibniz to deliver to Leeuwenhoek.