This problem has been discussed in the past. For example, in this topic:
Can bitcoin be divided beyond satoshis?.
This answer is just a possible suggestion:
Currently you are not able to divide it beyond as satoshi is the smallest introduced unit. However, if it ever becomes needed, additional units could be added that are smaller than a single satoshi (e.g. 1 000 000 Laudas = 1 Satoshi). I don't think that it will come to that though.