Why can you see the parts of a onion under a microsope?

You can see the parts of an onion under a microscope because onion cells are relatively large and have distinct cell structures, such as the cell wall, nucleus, and cytoplasm. The onion's transparent cell walls allow light to pass through, making it easier to observe the details. Additionally, when stained, the cells become more visible, highlighting various components under the microscope. This combination of size, transparency, and staining makes onion cells ideal for microscopic examination.