Thank you Clusiana! It is a very precious miniature tulip, I bought it from a Dutch Bulb nursery called Peter Nijssen.
Unfortunately I lost them last winter, not because of the cold as it is very hardy but because I had it in a pot that got too wet.
I'm sure it would do very well in full and very well drained soil in the sun or half-shadow.
I just discovered that the name should be Tulipa humilis 'little Luna', I'll have to change that in the database..