When you don't have an actual tree but you do have a board and plenty of chalk.

#LabTree

A couple of years ago my roommates and I had a party where we asked everyone to bring something for the tree. That is how we ended up with a chlamydia Christmas tree. Thanks @GIANTmicrobes for making this tree possible! #gradschoolchristmastree #labtree #sciencechristmas #microbe