This presentation provides a brief, non-technical introduction to Engel's law, one of the most important empirical regularities in economics. This regularity was established by German statistician Ernst Engel in 1857 using budget data from Belgian households, and states that the share of total household expenditure allocated to food decreases as the level of household income increases. The regularity has been proven to hold in a variety of contexts, and this presentation contains examples from a cross section of countries, from households in different deciles of the income distribution for a given country, as well as over time for a given country.