While early robots were utilized in factories to perform repetitive, dangerous, heavy or dirty jobs from within protective shells, nowadays they interact with people on the physical, cognitive and emotional level. Robots are still used in production lines and hostile environments, such as in outer space and the depths of the sea, in war or rescue operations. Today, however, many different types of robots are present in the places inhabited by humans including: cars, vacuum cleaners and lawn-mowers, toys, assistive devices for the elderly and disabled persons, diagnostic, rehabilitative and surgical tools, and prostheses. The form of the robot changes according to its use. They can appear as household electrical appliances, or take on animal-like or human-like forms. They are made up of different materials, from "traditional" iron and silicon to silicone, biological molecules (nanorobots) and barcodes (software robots).