Micrographia of the twenty-first century: from camera obscura to 4D microscopy

Abstract

In this paper, the evolutionary and revolutionary developments of microscopic imaging are overviewed with a perspective on origins. From Alhazen's camera obscura, to Hooke and van Leeuwenhoek's two-dimensional optical micrography, and on to three- and four-dimensional (4D) electron microscopy, these developments over a millennium have transformed humans' scope of visualization. The changes in the length and time scales involved are unimaginable, beginning with the visible shadows of candles at the centimetre and second scales, and ending with invisible atoms with space and time dimensions of sub-nanometre and femtosecond. With these advances it has become possible to determine the structures of matter and to observe their elementary dynamics as they unfold in real time. Such observations provide the means for visualizing materials behaviour and biological function, with the aim of understanding emergent phenomena in complex systems.

Figure 1.

The significance of the light–life interaction as perceived more than three millennia ago, at the time of Akhenaton and Nefertiti. Note the light’s ‘ray diagram’ from a spherical source, the Sun. Adapted from Zewail (2008).

Figure 2.

The concept of the camera obscura as perceived a thousand years ago by Alhazen (Ibn al-Haytham), who coined the term (see text). Note the formation of the inverted image through a ray diagram. Adapted from Al-Hassani et al. (2006).

Figure 3.

Microscopy time line, from camera obscura to three-dimensional electron microscopes. 4D ultrafast electron microscopy and diffraction were developed a decade ago (see text). The top inset shows the frontispiece to Hooke’s (1665)Micrographia published by the Royal Society of London. In the frontispiece to Hevelius’s Selenographia (bottom inset), Ibn al-Haytham represents Ratione (the use of reason) with his geometrical proof and Galileo represents Sensu (the use of the senses) with his telescope. The two scientists hold the book’s title page between them, suggesting a harmony between the methods (Sabra 2003; Steffens 2006; Zewail & Thomas 2009).

Figure 4.

Resolutions in space and time achieved in electron microscopy. The focus here is on the comparison of ultrafast electron microscopy (UEM) and transmission electron microscopy (TEM), but other variants of the techniques (scanning EM, tomography and holography, as well as electron spectroscopy) can similarly be considered. The horizontal dimension represents the spatial resolution achieved from the early years of EM to the era of aberration-corrected instruments. The vertical axis depicts the temporal resolution scale achieved up to the present time and the projected extensions into the near future. The domains of ‘fast’ and ‘ultrafast’ temporal resolutions are indicated by the areas of high-speed microscopy (HSM) and ultrafast electron microscopy (UEM) (Zewail & Thomas 2009). Vertical dotted lines separate the spatial resolutions characteristic of real-space (microscopy) imaging from the spatial resolutions that are obtainable using the reciprocal-space (diffraction) techniques, which reach the picometre scale.

Figure 5.

4D electron imaging in real, Fourier and energy spaces. The conceptual design of Caltech’s UEM-2 is presented on the right; a single-electron trajectory is depicted within the UEM. The atomic-scale (femtosecond) temporal resolution characteristic of the apparatus allows for the visualization of dynamical processes in real time. Shown on the left are typical UEM frames of real-space images and diffraction patterns, together with three-dimensional maps of femtosecond-resolved electron-energy-loss spectra (FEELS). For a recent review, see Shorokhov & Zewail (2009).