We do not just cooperate within mathematics: we make significant contributions also to physics, biology and technology.
Here is a sample.

SWI stands for `Studiegroep Wiskunde met de Industrie'. Every year a number of Dutch experts meets for one week to help solving a number of problems raised by business. Examples of recent topics: Pumps to help hart patients, Writing computer chips with a beamer, Option prices in a formula, Increased yield in a closed greenhouse, Smart use of KLM-reservecrews, Less noise in MRI-images. In the beginning of 2015 the Mathematical Institute was the host of this event.

In recent years there has been a recurrent problem of outbreaks of infectious diseases, both of animal and of human origin. Early detection and mathematical analysis of the course of  an outbreak can prevent lots of suffering and economic damage.  Members of the MI collaborate within UCID (Utrecht Center for Infection Dynamics) with scientists from RIVM, the UMCU and the veterinary faculty of Utrecht University. This has lead to new knowledge and insights.

The Department of Mathematics and RIVM have set up a collaboration to establish a fluid exchange of both expertise, students and  possibly researchers.  For the department of Mathematics, this is part of a  long-term project of developing mathematics for health and medical applications. For RIVM, it opens up possibilities to make  the expertise of the members of the department available for strategically relevant issues.

We have a purely scientific cooperation with CWI, the `Centrum voor Wiskunde en Informatica' in Amsterdam. Exchange of personel - with one of our professors spending one day a week at  CWI, and a senior researcher from CWI visiting the MI - has proved to be quite fruitful. It leads  to more frequent and  interesting publications.

The  History of mathematics group cooperates with several institutes abroad in the area of education of mathematics (e.g. the  House of Mathematics at Isfahan, Iran). It organizes historical workshops that attract a wide audience.

Discoveries in the biological and biomedical sciences increasingly require combining sophisticated technologies, quantitative measurements, and theoretical approaches such as bioinformatics, mathematical modelling and computer simulations. Hence, modern Life Sciences research faces the challenge to integrate different scientific disciplines and foster collaborative projects between biologists, chemists, physicists, computer scientists and mathematicians to make biology a quantitative natural science.That is why we take part in the Master program Quantitive Biology & Computational Life Sciences (QBio)