Miso is a foodstuff made of fermented soybeans, used in making miso soup.
Miso can be written in Chinese characters as . This usage is a peculiar one. The first character means 'flavour' but the second means 'noisy'. The characters appear to have been chosen for their sound. This usage is found in the following sign:
However, it is probably more common to write miso in hiragana, as in the following sign:
In restaurants, it is also common to write words in katakana, as in the following:
What is interesting in this case is that all three examples come from outside the same restaurant!
A Google search in August 2003 reveals the following distribution of usage:
The katakana form often also has the meaning 'key point' or 'nub'.