I’ve always noticed that my best ideas come while I’m in the shower. I suspect I’m not the only one. When I’m in the shower problems suddenly become simpler to solve, thoughts are clearer, and planning is easier.
It’s not hygiene that makes it happen. It’s the state of relaxation and low levels of stress that frees up our minds.
I guess the most famous case of innovation in a bathtub can be attributed to Archimedes. He reportedly proclaimed "Eureka!" when he stepped into a bath and noticed that the water level rose—he suddenly understood that the volume of water displaced must be equal to the volume of the part of his body he had submerged. He is said to have been so eager to share his discovery that he leapt out of his bathtub and ran through the streets of Syracuse naked.
Another known legend is that Sir Isaac Newton’s discovery of the force of gravity came while he was resting under an apple tree and observed as an apple fell to the ground.
Whether these are simply great stories or actual historic events is not important. Research has shown that our brains operate best when we are relaxed and our minds are clear of negative stressful thoughts. This state of relaxation allows our brains to think more clearly, as well as wander freely, which leads to more creative thinking.
Such a state of relaxation can be achieved in several ways, including yoga, meditation, and being outdoors in the nature. Perhaps the easiest way is simply taking a nice long shower or bath.