HEK 293 cell culture - (Nov/16/2011 )

Hi every body
i ma using HEK293 cells after overnight incubation usually when i cheked by cells on high magnification i saw some small particles moving in the medium?? I am not sure what is this my medium is clear, some body said to me this is nuclear or cell debris but if it is debris why it always continue on moving like some bacteria etc. i am very much confused on normal magnification the cells looks very good
if you have some idea please help me to get out from this confusion

Google "brownian motion"

Thankyou so much you solved my problem but how can i prevent this motion in my cells??

You can't, unless you can cool them to absolute zero (0 Kelvin), it is a result of the motion of molecules which have some heat energy.