Scientists use the word 'sample' to describe an object that is being observed under a microscope. A sample can be anything from an insect to a drop of pond water or a piece of fabric. A sample can be the whole object or just part of the object. For example, both an entire leaf and just the stem are considered samples. When you collect samples from outdoors, remember to choose carefully.
Nature has a delicate balance, and can be easily damaged.
Take only the smallest quantity that you need and be selective in how you choose. If you are looking for a leaf sample, whenever possible take a leaf that has already fallen to the ground rather than one that is still on the tree. Notice how much of a sample is available. If you see only one sample of a particular plant, leave it behind to reproduce so perhaps next time you'll see more. And finally, when observing insects, try to find samples that are already dead.