A microscope is an indispensable tool for biologists and researchers working with living organisms. By magnifying small specimens, a biological microscope allows observation of cellular and sub-cellular structures that are invisible to the naked eye. There are many types of microscopes developed for different purposes, but all share the goal of revealing the intricate details of life through magnification. This article will explore the basic components, functions and applications of biological microscopes in science.

Optical Components

All microscopes utilize a combination of lenses to magnify specimens. The objective lens closest to the sample is what determines the highest useful magnification. Common objective lens magnifications are 4X, 10X, 40X and 100X oil immersion. Light from the specimen passes through the objective and eyepiece lens, which contains additional lenses to further magnify the image for viewing. Condenser lenses below the stage illuminate translucent samples with transmitted light.

Light Pathways

Biological microscopes often employ alternative light pathways for different visualization needs. In transmission biological microscope, light shines up from below the stage through transparent specimens. In brightfield mode, structures absorb and transmit light to appear dark or light. Phase contrast instead converts phase differences into intensity differences, revealing subtle details. In dissection microscopes, oblique light from the sides illuminates opaque specimens. Fluorescence variants use specific excitation light wavelengths absorbed by markers to glow-fluoresce particular structures.

Resolution and Depth of Field

Microscope resolution can detect features down to approximately 200 nanometers using the highest objective lens magnifications of around 100X. However, limited depth of field constrains sharp focus to a thin plane - reducing focus depth as magnification increases. Adjusting the fine focus knob precisely focuses the desired plane into view. Objectives with longer working distances provide deeper focus range at the cost of magnification power.

Mechanical Design

Most microscopes feature robust bases or frames supporting the stage and optics. Coaxial coarse and fine focusing knobs raise and lower the stage for gross and precise focusing. The optical tube or body routes light up from the stage to the ocular lenses or cameras. Trinocular heads connect to cameras for live imaging with a third ocular tube. Arms or flexible goosenecks hold transmitted light sources below stages. Movement controls hold slides under the objective paths. Sturdy yet precise mechanics ensure reliable image clarity.

Applications in Biology

Common microscope applications include studying cellular structures, organelles and internal components. Cell biology examines mitosis, cytokinesis, motility and internal activity at the subcellular level to better understand functions. Physiology compares cell and tissue types between species or under different conditions. Anatomy identifies components in complex biological systems like nervous, reproductive or circulatory systems. Histology prepares microscopic cross sections of embedded plant or animal tissues for structural analysis. Forensics compares hair, fiber and other trace samples to crime scene evidence. Genetics analyzes chromosomes and genetic material at high magnification. Microbiology cultures and identifies pathogens, parasites and other microbes impacting health or industries. Ecology explores microscopic flora and fauna interactions across ecosystems. Behavioral studies examine microscopic lifeforms to better understand complex populations over multiple genetic generation