Nature Highlights article on the Journal of Brief Ideas, which itself is brief.
According to the Journal FAQ, submitting such brief reports is part of establishing something below the current standard for the minimal publishable unit. It is also important for enforcing good scientific citizenship practices . Very short papers have occasionally been published in regular journals. Mathematics papers by Lander and Parkin  and Conway and Soifer  accomplished mathematical proofs in less than a paragraph (but with multiple figures). Other than these rather mythical examples, it is quite the challenge to integrate a well-formulated idea into the Journal of Brief Ideas' 200 word limit.
 Woolston, C. (2015). Journal publishes 200-word papers. Nature, 518, 277.
 Indexing done via document object identification on Zenodo, doi:10.5281/zenodo.167647
 If a picture is worth 1000 words, then the Journal of Brief Ideas become less brief than its name implies.
 Neisseria (2015). All you need to publish in this journal is an idea. Science Made Easy blog, February 13.
 Lander, L.J. and Parkin, T.R. (1966). Counterexample to Euler's Conjecture on sums of like powers. Bulletin of the American Mathematical Society, 72(6), 1079.
 Conway, J.H. and Soifer, A. (2004). Can n2 + 1 unit equilateral triangles cover an equilateral triangle of side > n, say n + ɛ? American Mathematical Monthly, 1.