organelles and gained an understanding of their functions. While some scientists were studying the functions of cells, others were examining details of their structure. They were aided by a crucial technological development in the 1940s: the invention of the electron microscope, which uses high-energy electrons instead of light waves to view specimens. New generations of electron microscopes have provided resolution, or the differentiation of separate objects, thousands of times more powerful than that available in light microscopes. This powerful resolution revealed organelles such as the endoplasmic reticulum, lysosomes, the Golgi apparatus, and the cytoskeleton. The scientific fields of cell structure and function continue to complement each other as scientists explore the enormous complexity of cells. Another busy area in cell biology concerns programmed cell death, or apoptosis. Millions of times per second in the human body, cells commit suicide as an essential part of the normal cycle of cellular replacement. This also seems to be a check against disease: when mutations build up within a cell, the cell will usually self-destruct. If this fails to occur, the cell may divide and give rise to mutated daughter cells, which continue to divide and spread, gradually forming a growth called a tumor. This unregulated growth by cells can be benign, or harmless, or cancerous, Mullinax3This may threaten healthy tissue. The study of apoptosis is one thing that scientists explore in an effort to understand how cells become cancerous. Scientists are also discovering exciting aspects of the physical forces within cells. Cells use a form of architecture called tensegrity, which enables them to withstand battering by a variety of mechanical stresses, such as the pressure of blood flowing around cells or the movement of organelles within the cell. Tensegrity stabilizes cells by evenly distributing mechanical...
