Chemical stimuli refer to substances that can trigger a response in living organisms. These stimuli can be found in various forms, such as hormones, neurotransmitters, or environmental chemicals. They play a crucial role in processes like communication between cells, regulation of bodily functions, and responses to external changes. In nature, organisms often rely on chemical stimuli to interact with their environment. For example, plants may release volatile organic compounds to attract pollinators or deter herbivores. Similarly, animals use chemical signals, like pheromones, to communicate with each other, influencing behaviors such as mating and territory marking.