| Technique | Principle | Resolution | Comments | Applications in spines and synapses | |
|---|---|---|---|---|---|
| Lateral (XY) | Axial (Z) | ||||
| CLSM | 250 nm | 500 nm | |||
| TPLSM | Two-photon excitation | 350 nm | 700 nm | Deeper tissue penetration; adaptive optics further improve | Helmchen and Denk, 2005; Ji, 2017 |
| STED | Stimulated emission (Vicidomini et al., 2018) | 20–70 nm | 500 nm | 3-D STED increases axial resolution; chronic in vivo imaging is possible | Nägerl et al., 2008; Berning et al., 2012; Pfeiffer et al., 2018 |
| SIM | Moiré effect with structured illumination (Wu and Shroff, 2018) | 100 nm | 250 nm | No need for special fluorophores; limited resolution improvement | Kashiwagi et al., 2019; Li et al., 2020 |
| SMLM (PALM, STORM) | Photoactivation, photoconversion (Baddeley and Bewersdorf, 2018) | 10–30 nm | 30–60 nm | High spatial resolution; temporal resolution is relatively worse | Dani et al., 2010; Tang et al., 2016 |
| ExM | Physical expansion of sample (Wassie et al., 2019) | 4–20-fold improvement | 4–20-fold improvement | Capable of combining with other imaging techniques, only for fixed samples | Gao et al., 2019; Sarkar et al., 2020 Preprint |
| Technique | Principle | Resolution | Comments | Applications in spines and synapses | |
|---|---|---|---|---|---|
| Lateral (XY) | Axial (Z) | ||||
| CLSM | 250 nm | 500 nm | |||
| TPLSM | Two-photon excitation | 350 nm | 700 nm | Deeper tissue penetration; adaptive optics further improve | |
| STED | Stimulated emission ( | 20–70 nm | 500 nm | 3-D STED increases axial resolution; chronic in vivo imaging is possible | |
| SIM | Moiré effect with structured illumination ( | 100 nm | 250 nm | No need for special fluorophores; limited resolution improvement | |
| SMLM (PALM, STORM) | Photoactivation, photoconversion ( | 10–30 nm | 30–60 nm | High spatial resolution; temporal resolution is relatively worse | |
| ExM | Physical expansion of sample ( | 4–20-fold improvement | 4–20-fold improvement | Capable of combining with other imaging techniques, only for fixed samples | |
CLSM, confocal laser scanning microscopy; SMLM, single-molecule localization microscopy; STORM, stochastic optical reconstruction microscopy; TPLSM, two-photon laser scanning microscopy.