Everything in the environment is a sensorial experience, some rich, some not so much....  We try to stay away from Plastic which has very little sensorial value.   What is hard, soft, cold, cuddly?  What sounds does this make when I set it down or pour this into that?  Why does this have a shine?  Does it have a smell?  Does it have a taste?  The best description in two words is "Little Scientist"   You can read my college papers on Sensorial at this site:monarchmontessori.tripod.com/id25.html