Here are some ideas for Apartment Greenhouses. 

IKEA SOCKER

IKEA

I just love how mini greenhouses look! Plus, I can put ferns in them, so the cats can't eat them. I have the SOCKER greenhouse from Ikea. 

Willab Garden - Balkongväxthus Juliana

I have been wanting to buy a bigger one for my balcony. But they are quite expensive. 

I have been also wanting to make a DIY Mini Greenhouse out of old picture frames. Like this one:

DIY Picture Frame Mini Greenhouse

This one is out of old windows and could be nice in a living room or balcony. 

Old Window Greenhouse

Another idea that I found recently was making a greenhouse out of an aquarium or reptile habitat. 

Boho Aquarium Greenhouse/Terrarium

DIY Greenhouse from an small aquarium. 

Old Aquarium Greenhouse

Do you have any more ideas? Have you ever made a mini greenhouse?