What a wonderful world …

eye

The human eye, Darwin argued, could have evolved from a simple light-catching patch of tissue of the kind that animals such as flatworms grow today. Natural selection could have turned the patch into a cup that could detect the direction of the light. Then, some added feature would work with the cup to further improve vision, better adapting an organism to its surroundings, and so this intermediate precursor of an eye would be passed down to future generations. And, step-by-step, natural selection could drive this transformation to increased complexity because each intermediate form would provide an ad–vantage over what came before. https://www.quantamagazine.org/the-surprising-origins-of-lifes-complexity-20130716/