generating low noise source of 100 microVolts to 1mV

Hello,

I want to design a voltage source of with voltage ranges from 100 microVolts to 1 mV. I want it for biomedical instrumentation(EEG/ECG). I was thinking of voltage divider but that would not work because of resistance and supply noises. Please suggest me some better way.

How about one of these? You can use a low value resistive divider with a potentiometer to get the voltage range you want.