This video lesson introduces students to the concept of size. It looks at how to classify objects based on their size and how the size of an object affects its properties and behavior. In our world, we have many different sizes - starting from quarks and subatomic particles, to atoms and molecules, all the way to aggregates and huge objects like ourselves, and beyond to larger bodies like mountains, planets, stars, galaxies and even to the whole universe. This lesson explores how size affects the properties of an object by affecting the amount of interaction taking place with the environment. Some of these affected properties are very obvious, such as solubility, while others are not. This lesson will take one class lesson of about 50 minutes, and there are no prerequisites. Materials needed include: beakers or containers that are transparent; small quantities of various materials (i.e. sand, chalk, sugar, salt, milk (liquid), lotions or any other material and beads); and a tool to grind solids. In-class activities during video breaks include class discussions, demonstrations with various solutions, and work with calculations.