Using the traditional instruments for measuring high frequency signal All we know that we can not use the probe for measuring the high-frequency signal (microwave signals). I still can not understand the reason. I have read that the reason because of the wavelength size of the microwave signals is comparable to the electronic components, but this does not make any sense to me as the wavelength of the 1GHz is about 20 cm which is already comparable to the size of the electronic components.  

Could any of you please explain to me in more details why we can not use the probe for measuring the high-frequency signal.
Not sure to understand what you are asking, Microwaves wavelengths range between 300 MHz (1 m) and 300 GHz (1 mm) which is indeed of the same order of magnitude as the probe. 

1GHz corresponds to a wavelengths of about 30 cm  and is also in the Microwave range. 

Are you saying that it is possible to measure a frequency of 1GHz with a probe while it is usually said that Microwaves can't be measured with it?