What type of microscopy can be used to examine living cells?

Phase contrast microscopy is the correct choice for examining living cells due to its ability to enhance the contrast of transparent and colorless specimens without staining. This technique allows for the visualization of cellular components and dynamics in their natural state, facilitating the study of living cells in real time. The phase contrast method works by using a special optical setup that converts phase shifts in light passing through the specimen into changes in amplitude or brightness, making the transparent structures visible.

While fluorescence microscopy is also a powerful tool for studying living cells, it typically requires the use of fluorescent dyes or proteins, which may not always be compatible with live-cell imaging. Electron microscopy, on the other hand, requires a vacuum environment and sample preparation that usually involves fixation and dehydration, making it unsuitable for observing living cells. Dark field microscopy can observe living cells and enhance contrast but is generally not as widely used for detailed studies of living cellular structures compared to phase contrast microscopy.