Fluorescent microscopy uses high-intensity light to excite fluorescent molecules (fluorophores) in biological samples. When excited, these molecules emit light at longer wavelengths, creating contrast against a dark background. Modern LED-based systems have replaced traditional mercury lamps, offering longer lifespans, consistent output, and reduced maintenance.
Automated fluorescence cell counting uses nuclear stains (like Hoechst or DAPI) to identify and count individual cells. More advanced systems can distinguish live vs dead cells using viability dyes, calculate confluence, and track proliferation over time without manual intervention.
Measuring the percentage of a culture vessel covered by cells is essential for determining optimal passaging times, normalizing experiments, and standardizing protocols. Modern imaging systems use phase contrast or fluorescence to calculate confluence automatically, reducing subjective human error.
Time-lapse fluorescence microscopy tracks cellular processes over hours or days. Onstage incubators maintain temperature, humidity, and CO2 levels, enabling studies of cell migration, division, differentiation, and drug responses in physiologically relevant conditions.
Green Fluorescent Protein (GFP) and its variants allow researchers to visualize protein localization, gene expression, and cellular processes in real time. Multi-channel systems can simultaneously track multiple reporters for complex pathway studies.
The right fluorescence microscope depends on your assay, throughput and budget. Entry-level systems such as the EVOS M3000 give you two fluorescence channels for routine GFP/RFP work. Mid-range and professional systems add more channels, automated counting and time-lapse. Our reviews focus on what matters for UK research labs: no pricing, no sales pressure, just qualitative comparisons. For a dedicated GFP microscope buying guide, see the best microscope for GFP imaging page.
A fluorescence image is only as good as the match between your fluorophore, excitation source and filter set. The table below lists common dyes used in UK cell-biology labs, their typical excitation/emission ranges and common applications. Use it to plan panels and avoid spectral overlap.
| Fluorophore / dye | Typical excitation | Typical emission | Common use |
|---|---|---|---|
| DAPI / Hoechst | ~350–370 nm | ~460 nm (blue) | Nuclear counterstain, cell counting |
| FITC / GFP / Alexa Fluor 488 | ~470–495 nm | ~510–530 nm (green) | Protein reporters, GFP assays |
| TRITC / RFP / mCherry / Cy3 | ~540–570 nm | ~580–630 nm (red/orange) | Co-localisation, second reporter |
| Cy5 / Alexa Fluor 647 | ~620–650 nm | ~660–700 nm (far-red) | Third/fourth channel, reduced autofluorescence |
It is used to visualise specific molecules, proteins or cell structures by exciting fluorescent dyes or reporters and detecting the emitted light. Common uses include cell counting, viability assays, GFP reporter imaging, protein localisation and live-cell time-lapse.
LED light sources last longer, are more stable, switch channels instantly and need almost no maintenance. Mercury lamps can still offer high intensity for demanding dyes but are being phased out in most modern cell-imaging systems.
Two channels are enough for most GFP/RFP co-localisation work. Four channels let you add nuclear stains and far-red reporters in one capture. Pick based on your typical panel, not on maximum channel count.
Some imaging systems include automated counting and confluence modules; others are imaging-only. See our automated cell counting microscope guide for which systems handle analysis on-board.
The EVOS M3000 covers two-channel fluorescence imaging for routine work. The EVOS M5000 adds four-colour fluorescence plus built-in automated cell counting and confluence. The EVOS M7000 adds automated plate scanning and Celleste analysis for high-content workflows. Compare them in our EVOS M3000 vs M5000 vs M7000 guide.
10× or 20× objectives are ideal for colony or well-level overviews and confluence. 40× is the standard for sub-cellular localisation. Higher magnifications need better NA and more stable focus; oil-immersion objectives give the brightest fluorescence but are slower to use in multi-well plates.
Use the lowest excitation intensity that still gives a usable signal, keep exposure times short, increase interval between frames, and add anti-fade supplements for fixed samples. For long time-lapses, far-red dyes photobleach more slowly than green reporters.
Most modern all-in-one cell-imaging systems use LED illumination, including the EVOS M3000, M5000 and M7000, the iOlight portable microscope and many Zeiss, Leica and Olympus inverted fluorescence configurations. Mercury lamp systems are now largely confined to older or specialist epifluorescence setups.