I cannot claim that this is an original idea. In fact, I saw a post on the hgtv garden blog about this project and just felt inspired. I loved the idea of turning regular old used jars with dumpy lids into very clever terrariums. I immediately had all kinds of ideas about how to adapt the lids to what I had on hand, since i didnt have little animal figurines, but then it occurred to me that I probably had many glass containers with lids from spent candles. Nice lids that I didn’t even have to get out the glue and spray paint for. I just needed some elbow grease to clean the soot and wax from the inside.
I chose this classy little jar with a pretty little lid and cleaned it up.
Then the terrarium practically made itself. I layered some small-ish pebbles and then a layer of organic garden mix.
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Then I went outside grabbed a couple of moss specimens from my backyard.
I placed the moss onto the dirt layer. 
I knew I wanted something else in there and debated digging up a small bulb like a grape hyacinth. But I settled on a couple of sedum tips. I had this nice purple sedum that will bloom with pink flowers–if it ever blooms.
I used a plastic knife to work the sedum into the soil. And then placed some small quartz pebbles and beach glass that I had picked up on some beach somewhere around he sedum.
I lightly watered–not even enough water to drain to the bottom–the sedum and moss and placed the lid on tightly. There should be enough moisture in the terrarium to keep the moss moist and sedum is pretty much the hardiest plant on the planet. I found this wonderful resource for moss management and feel confident that the plants I chose will be low care. 
I adore the way it turned out and it was an easy project that I didn’t have to buy a single thing for. Don’t you just love upcycling items with nature’s help!? I do!
Life Improved 
After the initial water I put in, it won’t need more water? Does it need sunlight or will it survive in my windowless office?
I hate to be so vague but you have to watch it for a few days to see how the moisture is inside the terrarium. Read this article for a great overview (exposure #7):
Click to access Terrariums%20K_2.pdf
You definitely don’t want to see water on the bottom in the pebbles because that just means the water will sit there and stagnate. And if the lid is not right then you will lose the moisture and destroy the atmosphere inside the jar. Then, again, you can always choose succulents and keep the jar open.
Keep the terrarium out of direct sunlight but in a room that gets light. It will probably take care of itself! I actually chose a plant that’s a bit too sturdy and it is growing rapidly. I may have to remove it soon and replace it with something really slow growing.
Oh–and to answer your windowless office question, choose plants that would do better in low to medium light situations. Think forest or jungle floor, or on understory plants that grow on trunks and trees, like spider plants, pothos, snake plants, dracaena, African violets bromeliads and ferns. Fluorescent lights are actually supposed to be pretty good for plants, but because you don’t know what kind of light spectrum the ones in your office emits, stick to plants that would do well in most situations. Now… The problem is you have a tiny terrarium! You need a tiny plant. Not one with a huge leaf. I would snip a co-workers spider plant and nestle it inside your terrarium. Bromeliads are slow growing and if you have an office mate with one you may be able to get a newly forming plant for your terrarium. If you have no ideas what you or your coworkers already have, take a picture and I can tell you–probably.