why can't we see germs?

Tonight was the first night Sophie has had a mom who was half-way involved in a meaningful way to help her get ready for bed since Saturday. For the last four days, I've been struck with strep throat.  I've never been so thrashed in my life-ever! Each day I'd be up enough to do the bare minimum and then back to sleep. After the diagnosis, of course, then the goal has been to not infect others in the house, which cuts back on any kind of cuddle time.  So tonight was the first night I've gotten to stay with Sophie for a few minutes before she fell asleep.  She asks crazy hard questions at this time.  Tonight, it was, "Why can't we see germs?"  Ugg, I don't know. Then I started wondering/suggesting that germs were like a bad kind of bacteria that we also can't see, then I realized I don't have a clue what I'm saying. So I start suggesting that when she's older she can work in laboratories to figure these things out.  She seemed more bummed out than excited, so I followed up with "You don't HAVE to work in the laboratories, only if you want to." That put her a bit more at ease. Then I went and washed my hands for about the 50th time today.