The major achievement of Dr. Makoto Fujita, professor at The University of Tokyo, in the last twenty-four years is the development of highly ordered discrete molecular frameworks by transition-metal directed self-assembly. His method is well featured by an extremely elegant use of the square planar coordination geometry of transition metals, which was first demonstrated in 1990 by the self-assembly of a Pd(II)-bipyridine square compound. This historical publication had an enormous impact on the molecular sciences in general, as testified by the number of reports on self-assembled 2D and 3D structures, incorporating transition metals and di- or multitopic ligands, published since this first paper. Subsequent, outstanding development of this work by Fujita himself is the extension of the square's two-dimensional (2D) framework into three-dimensional (3D) frameworks like cages, capsules, bowls, tubes, spheres, and catenanes. Extremely simple procedures (only mixing the components in solution!) strikingly dominate over the tedious ones of previous covalent syntheses. The results enjoy its unique status for (i) the facile creation of large hydrophobic cavities, (ii) very strong binding of neutral molecules in the cavities, and (iii) unprecedented physical and chemical phenomena within the cavities. Amongst his many significant contributions to molecular science, the following achievements rank as some of the most highly original ones.

1. Metal-Mediated Assembly of Macrocycles and Catenanes.
Most of the macrocycles thus obtained showed remarkable ability for the molecular recognition of neutral molecules in aqueous media. Fujita also discovered in 1994 the spontaneous and quantitative formation of catenanes from two preformed metal-linked rings, reminiscent of well-known "magic rings". The principle in Fujita's catenane synthesis is quite unique in that it does not need any template and the catenane formation from the component rings is reversible. The wide applicability of the self-assembly synthesis of catenanes has been further demonstrated by the spontaneous formation of highly sophisticated interlocked molecules like a doubly interlocked (four crossing) catenane and a three-dimensional catenane composed of two identical cages.

2. Three-Dimensional (3D) Assembly by Molecular Paneling
Fujita's outstanding molecule that strongly impacted supramolecular communities is an M₆L₄ type cage. The cavity of this cage is extraordinarily large, being able to bind as many as four large molecules like adamantane, o-carborane, or ferrocene. Facile synthesis of this cage by self-assembly as well as its unique properties (as discussed later) has promise for potential applications and led to the commercial production of the cage with 100-g scale synthetic procedure. Fujita's immediate development of this result into the general strategy for the self-assembly of a variety of 3D structures deserves particular attention. He has designed a family of molecular panels with the basic shapes of triangles, squares, and rectangles. The assembling of these panels by clipping with Pd(II) 90°-blocks provided a new strategy that he terms as "molecular paneling".

3. Function through Architecture
Fujita's self-assembled cages also dominate over previous organic receptors in their molecular recognition ability. The cavities are extraordinarily large and are capable of binding neutral guests. Through molecular recognition, extremely elegant and fascinating functions are created from his self-assembled architectures.

• Molecular Recognition: As many as four large guests (e.g., adamantane, carborane) are encapsulated. Two different guests can be accommodated in a pairwise selective fashion, facilitating reaction design in the cavity. In the recognition of biomolecule fragments (oligopeptides or short nucleotides), their in vivo structures are reproduced in the cages in water.
• Cavity-directed Synthesis: Reactivity and catalysis controlled by cavities represent one of the most important functional properties of self-assembled hosts. Fujita has pioneered such functions with the large cavity of the self-assembled cages. The photodimerization of olefins as well as Diels-Alder reactions in the cage are featured by remarkable rate enhancement (>10² times), perfect regio- and stereo-selection, high pairwise selection, and even by chiral induction up to 50%ee. Notably, unreactive aromatics, even naphthalene, smoothly undergo the Diels-Alder. In a single crystalline state reaction, extremely unstable reaction intermediate generated in the cage can be examined by X-ray analysis.
• New physical properties: Spin-crossover, stable organic mixed valent states, metal-metal bonding, spin-spin interaction, photo-induced guest-host electron/energy transfer have been observed through the accommodation of appropriately designed substrates.

4. Dynamic Self-Assembly
Fujita first designed the guest-induced assembly of a cage in 1995. The scientific significance of this phenomenon is the demonstration that any substrates potentially have the ability to induce the formation of their optimal receptors, providing the basic principle of dynamic receptor library, which was later established by J. Sanders and J.-M. Lehn.

5. Spheres with Protein Size Cavities
Most spectacular topics in recent Fujita's works are the self-assembly of 5-nm sized M₁₂L₂₄ spheres and "EndoChemistry" developed at the endo-surface and inner space of the extraordinarily large shell compounds. Since any synthetic hosts have never possessed 5-nm sized well-defined cavities, the EndoChemistry has been creating many new concepts and methods. Discrete inorganic synthesis was demonstrated by the precise endo-template synthesis of silica in the sphere. The sphere can encapsulate even a protein within the shell, providing potential methods for controlling protein functions and for protein structure determination.

6. Porous Coordination Network
Since 1994, Fujita has also strongly contributed to the field of porous coordination networks, where he is trying to translate the solution chemistry of discrete cages into the solid chemistry of infinite porous materials while keeping the nature of the cavities identical. In his publication in 1994, he proposed the concept of "coordination zeolites"; this was done at the very early stage of MOF field (even term MOF was not invented). Hence the paper (JACS, 1994, 116, 1151) has been one of the most cited in this field (times cited: ~1900). His persistent endeavor in this field is to unambiguously confirm the events in the pore by X-ray analysis. A variety of organic transformations and even reaction snapshots including intermediate species have been observed.

7. Summary
In summary, Fujita has pioneered a novel principle of metal-directed self-assembly and developed their functions. He is undoubtedly an outstanding scientist who has brought molecular chemistry toward the next generation. The spectacular aspect of Fujita's chemistry has also an important impact on the way molecular chemists can present their field and make it attractive to a general audience. Citation is an important indicator for his scientific achievement. According to ISI Web of Knowledge, Makoto Fujita is a "Most-Cited Scientists in Chemistry" (around 19,000 citations). His h-index is equal to 74. Accordingly, it was approved that his achievements merit the Chemical Society of Japan (CSJ) Award.