I love a bit of history, and the most recent snippet I learned in Grasse was that the main square used to be the location of a tannery, which is actually how Grasse came to be the centre of the perfume world. The smell of tanned hides is pretty unpleasant (that's an understatement: the smell of the actual tanning process is putrid, and in the olden days, before things became more sophisticated, the tanned leather itself didn't smell too great either), so essences were used to mask the odour. Perfumed gloves became a popular local product, until the fashion for those faded in around the 18th century, and the focus became perfumes alone.
If you're interested in perfumes, I'd recommend both the Fragonard museum (do the tour, it's fun!), and the recently renovated Musee Internationale des Parfumeries. The perfume-making process is explained, and you get a sense of the history of perfume from ancient Egypt all the way to the 21st century. Perhaps my favourite thing to see is the collection of perfume bottles and labels, especially the Art-Deco era examples.
It can feel sometimes like Fragonard has taken over the whole of Grasse, but on the other hand, I absolutely love what they do. They make such beautiful things: sets of soaps in lovely decorated boxes, individual brightly coloured glycerine soaps, perfumes in the traditional tin canisters. Their homeware and jewellery stores (just up the street in separate stores from the museums) are also gorgeous, with beautifully selected linens, scarves, and quilts, amongst other things. Fragonard also owns the lovely Cafes des Musees (below).
One of these days I'll do a comprehensive visitors guide to Grasse and the surrounding area, since I go there so often!