3D Printing, Advertising, Cloud Storage, Trains, Mammals, Aerosol spray, Common Cold. Find out about the inner workings and origins of the things that pique your curiosity. 3D Printing: 3D printing is the process that creates three-dimensional objects by forming layers of material through computer control. Advertising: Advertising is a form of marketing communication that aims to promote or sell a product, service, or idea. Cloud Storage: Cloud storage is a set of logical pools in multiple servers where digital data can be stored. Train: A train is a form of transportation that usually consists of two or more vehicles connected to each other, and runs on a track. Mammals: Mammals are vertebrates from the class Mammalia, which comes from the Latin word "mamma" meaning breast. Mammals include the largest and smartest animals in the planet. Aerosol Spray: Aerosol spray is a dispensing system that creates an aerosol, a mist of liquid particles. Common Cold: Common cold is a viral infectious disease of the upper respiratory tract that mainly affects the nose and sometimes, the throat, sinuses, and larynx or voice box. It is also more simply known as a cold.