Solar activity as seen in x-ray wavelengths | NASA image gallery images.nasa.gov
The electromagnetic spectrum (EM spectrum) is what scientists call the range of different frequencies of energy released and absorbed by objects – known best to us as the visible light we can see and the infrared heat we can feel from the Sun (if it ever stops raining this summer).
For the parts of the EM spectrum that we can’t see, we have to design and use technology that can. Each wavelength is more suited to looking at particular scales of objects; long radio waves are suitable for probing deep into space at far off planets and black holes and x-rays in massive synchrotrons are used to diagnose tiny engine faults in F1 engines.