Congratulations on your new "TINY" family member!
That's a "house-mouse".
I hope he continues to stay healthy for you. Just don't even think of getting shots for him till he's at least 14 weeks old. I'd also have a tube of Nutri-Cal and give him a dime size a couple times a day. I'd say "after" he ate his breakfast and dinner. (of course he should be eating 5 to 6 tiny meals a day too. )
http://www.wholisticanimal.com/petvaccinations.html http://www.chron.com/cs/CDA/story.hts/front/1377004