Thank you all for comments.
Ecki,
It was really difficult to take photograph without moving diatoms. It is very frustrating when you are taking, for example, 20 th shoot and suddenly some Navicula is swimming across the field of view. Everything must be done from the beginning. So I'm happy I've managed to take this photograph.
Curt,
I usually try to catch microorganisms in general environmental context
So sometimes the entire image can remind a landscape.
Marek