Rain clouds

It makes sense that rain clouds are darker because they hold more moisture or droplets. Here's my question: What holds the rain droplets in the cloud, why do they accumulate and not just drop out as they gather?

Hi ykcir00222, if I am not mistaken, the clouds are made up of water droplets. For a regular cloud, it contain not much of water droplets, thus the sunlight can penetrate through it easily. When the cloud become full of water droplets, the sunlight cannot penetrate through it. That is why it appear dark to us. Correct me if i am wrong =)

If I am remembering correctly, the more condensation that a cloud holds, the darker it becomes. So, when a cloud is full and ready to release rain, it is darker that a cloud that doesn not hold as much moisture. Even clouds can only hold a certain capacity before they have to let loose.