Thanks for replies. Tubavykas, I thought clouds form for the same reason of the fog formation which occurs when temperature drops to reach dew point near ground (no space for more water).
From what I understood from your post, cloud formation is different and has nothing to do with air being saturated, but it is the cold air (at high altitude) loses the ability to hold water, so any ascending watervapor will not find a support from the upper cold air so it will condense.
Please correct me if I misunderstood and if I am correct, can you help me imagining why cold air loses the ability to hold watervapor as warm air? Thanks