When you hit the render button in Blender, you will start to wait for your image to appear in front of you for a little while. Depending on the number of samples, hardware a scene complexity it may take from minutes to hours. After that period you still might have to do some tweaking to remove all noise from the images altogether.
The noise in renders from Cycles and Eevee is something that you should plan to avoid having to spend time after render to post-process all images from a project. Using tools like the Denoiser is a great help, but doesn't solve complex scenes.
If you own an NVIDIA card and want to use Artificial Intelligence to reduce noise in renders from Blender, you should try D-NOISE. It is a free tool that uses your GPU to process and clean images with an incredibly low number of samples.
In their demo, you will see renders with no noise using just 100 samples. That number would never produce a noiseless image in Cycles.
You can check their demo video describing how the tool works.
The best part of that it can reduce noise from all types of images using the UV/Image Editor window of Blender. You can even get renders from other softwares and pictures.
Unfortunately, it doesn’t work with AMD cards.
