Soft matter science is concerned with soft materials such as polymers, colloids, liquid crystals, and foams, and has emerged as a rich interdisciplinary field over the last 30 years. Drawing on physics, chemistry, mathematics and engineering, soft matter links fundamental scientific ideas to everyday phenomena. One such example is "polymers", encountered in plastic materials and melted cheese, which illustrate how "sliminess" emerges from the flow and form of giant molecules. This Very Short Introduction delves into the field of soft matter, looking beneath the appearances of matter into its inner structure. Tom McLeish shows how Brownian Motion - the random local motion of molecules that gives rise to "heat" - is an underlying principle of soft matter. From hair conditioner to honey, he discusses how the shared physical properties and characteristics of these materials influence the way they behave, and their industrial applications.