**1. Introduction**

Pesticides are substances that exist in our daily lives. Their most widespread use is in agriculture, where they are used to protect crops from pests caused by plants and animals. They are also used to prevent diseases caused by ectoparasites in farm animals and pets. These substances are used in gardening and brought into our homes to protect us from mosquitoes and other insects. Pesticides come into intimate touch with all forms of life through drinking water and eating food. However, the use of these substances is so widespread and poorly controlled that environmental contamination is inevitable.

Pesticide exposure occurs in a variety of ways. Not all living organisms are exposed to the same periods or the same dose, or not even to a single type of pesticide or to the same mixtures. The above may have yet unknown, synergistic, or potentiating effects on organisms.

Insecticides are a class of pesticides used to kill or control insects. It is not only used in agriculture, but also in ornamental gardens, homes, and veterinary medicine. Although the hazardous effects on the environment and the health of living beings are not yet fully understood, they have become one of the primary solutions for crop protection in agriculture. Regardless of the fact that pesticides come in a wide variety of families, the major goal of this chapter is to highlight the effects of imidacloprid (neonicotinoid), chlorpyrifos (organophosphate), and carbaryl (carbamate), insecticides widely used in agriculture, despite recent findings of their neurotoxic effects on several animal species.
