OK I made another instructable about how to build a large essential oil extractor, this is a smaller version of that you can do on your stove.
BUT let it be known, this makes a incredibly small amount of oil.
This is ow it basically works, steam goes through the plant material this separates the oils and water form the plant material with the steam.
The steam then raises then condenses on the bottom of the large metal bowl, the drips into the small metal bowl, this water is called hydro sol, floating on the top of that is the plants oil.

Step 1: Things You Will Need

A Large metal bowl
a small metal bowl
a three part steamer pot
(commonly used for seafood)
a glass container
ice
plant material

Step 2: Step One: Big Bowl of Ice

First fill the large bowl with water and freeze it,

Step 3: Step Two: Gather Your Plant Material

Take you plant material this could be anything i used pine needles, normally i would use mint or lavender but its winter so all i had was pine needles for this demo. This is good for pretty much scented candles.
or aromatherapy.

Now fill the bottom of the steamer pot with water

Then fill the second layer of the pot with the pine needles and stems

Step 4: Step Three: Assemble the Steam Distiller

Ok Now you have the bottom pot filled with water the second layer filled with your plant material (i e pine needles)
but i suggest using some thing like mint or lavender or some kind of herb.
Then the Top layer of the pot you but in the center a small metal bowl
(only use metal anything else may explode)
Now on top of that you put on your large metal bowl of frozen water

Step 5: Step Four: Turn Up the Heat

Ok Now your distiller is all set up turn on the stove on high and let it boil
You want to boil out 99% of the water in the bottom of the pot.
This will take about 3 hours, make sure not to boil the water completely out if the pot burns this will destroy any oil you try to make
Once the ice in the large metal bowl melts and starts to get warm, replace the water with cold water and keep boiling it

Step 6: Step Five: Separating the Oil From Hydrosol

Ok After 99% of the water has boiled out of the bottom pot turn off the heat, and take of the large bowl, the remove the small metal bowl, the water in this bowl is now called hydro sol .
Take that water and let it cool, then let the plant material drain a little into the bottom pot.
Then take the remaining water and pour it into a glass container with the hydro-sol. (make sure this is all cooled down before you do this)
ok now you can toss the plant material, (great compost)
and you have a glass container with hydro sol and essential oil.
The oils since lighter then water will settle to the top, the easiest way I've found to separate the two is to freeze it.
The hydro-sol (water) on the bottom will freeze solid. The oils that wont freeze, can be poured off the top.
And there you go, you made a tiny bit of essential oil, its not much. But the hydro sol can used for alot of things and retain the sent of what ever plants you just used.