The purpose of this assessment probe is to elicit students’ ideas about the size of cells. It can be used once students understand that all organisms are made up of cells and to determine whether students recognize how small a cell is relative to other things. Early elementary students use magnifying lenses to observe parts of living things that are too small to see clearly with their naked eye. Upper elementary students are just beginning to learn about cells and use simple microscopes to observe them. Middle school students view a variety of cells and small parts of organisms and objects. They can interpret what they see under a microscope, can determine the magnification of their view, and begin to connect the size of cells to numbers that are much smaller than a millimeter. High school students transition from the whole cell to looking at structures within the cell. They learn about the molecules that make up a cell. Teacher notes, standards, assessment, and references are provided. This book selection also includes the Table of Contents, Dedication, Preface, Introduction, and Index..