De Kat (the Cat) is a working dye mill, one of the several windmills we saw in operation when we visited Zaanse Schans. In the first stage there are vertical cutters to chop up the raw material, and the millstones which then grind the pigment weigh in at 3 - 4 tonnes each. In the original design, there were wooden walls to box in the millstones processing different colours, to avoid cross-contamination.
You can get up close and personal with the huge cogs that drive the millstones, and we heard that a Japanese tourist was thrown through the air after grabbing hold of one of the windmill's powerful sails for a photo. It's certainly easy to imagine losing a limb if you worked here.
We visited on a very windy day, which is surely good weather for seeing windmills, and meant we had chance to watch the mill operative adjusting the sails.