I just introduced this to my soon-to-be-4 year old daughter. She really enjoyed it, as I thought she would, and it is a simple traditional Montessori lesson, easy to put together. Traditionally, there are six scents (12 bottles in all) but we started with 4 scents. The object is for the child to match the scents. Our bottles contain: lavender, cocoa, cinnamon, and vanilla. I used the cotton in all of the bottles in order to hold the scent, cover the contents and provide unity in appearance. The stickers help provide clarity during the activity.
I demonstrate (this activity is done on the floor using a rug) by setting up the bottles as shown. I choose the top left bottle, remove the lid and smell the contents. I offer the bottle to my daughter to smell and I then place it in between the two rows. I choose the top right bottle, remove the lid, smell and offer it to my daughter. I thoughtfully and silently shake my head "no" if it isn't a match after smelling and return it to it's spot. I then choose the second one down on the right and so on until a match is found.
When a match is found it is placed in the middle.
Each matching scent has a colored sticker under the lid. (Cinnamon blue, cocoa red....) When all the matches are found we tip the bottles to check under the lids to see if the stickers match, indicating it is a correct match. (I usually put the stickers on the bottom of the bottle but for some reason they kept falling off, hence the sticker under the lid.) Also, I would have used no lids if I had kept these spice bottles shaker tops (with the holes). Spice bottles with holes in the top or salt/pepper shakers work well for this.
This activity can rotate scents seasonally (which I will try to do)- pine needles in the winter, basil in the summer...
Also, a younger child who may not be able to match scents could be given one set to just smell. It is really an interesting activity that develops and awakens the olfactory sense.