Hydrogen and helium nuclei form in the first three minutes, with perhaps another 300,000 years before they combine with electrons to form atoms

As gravity exerts its pressure within parts of the expanding fireball, subnuclear particles merge into more complex elements

Empedocles states that all matter is made up of four elemental substances - earth, fire, air and water

The Greek philosopher Democritus declares that matter is composed of indivisible and indestructible atoms

A Greek text, attributed to Polybus, argues that the human body is composed of four humours

Epicurus postulates a universe of indestructible atoms in which man himself is responsible for achieving a balanced life

The first alchemists, working in Alexandria, are also the world's first experimental chemists

A Chinese manual on warfare includes the earliest known description of gunpowder

The Dutch chemist Jan Baptist van Helmont suggests that there are insubstantial substances other than air, and coins a name for them - gases

British chemist Robert Boyle defines the inverse relationship between pressure and volume in any gas (subsequently known as Boyle's Law)

German chemist Georg Stahl coins the name phlogiston for the substance believed to be released in the process of burning

Swedish chemist Georg Brandt discovers a new metallic element, which he names cobalt

The Swedish chemist Alex Cronstedt identifies an impurity in copper ore as a separate metallic element, which he names nickel

Scottish chemist Joseph Black identifies the existence of a gas, carbon dioxide, which he calls 'fixed air'

English chemist Henry Cavendish isolates hydrogen but believes that it is phlogiston

Swedish chemist Carl Wilhelm Scheele isolates oxygen but does not immediately publish his achievement

English chemist Joseph Priestley isolates oxygen, but he believes it to be 'dephlogisticated air'

French chemist Antoine Laurent Lavoisier publishes a system for classifying and naming chemical substances

English chemist John Dalton reads a paper describing his Law of Partial Pressure in gases (discovered in 1801)

At the end of his Partial Pressure paper, John Dalton makes brief mention of his radical theory of differing atomic weights

English chemist Humphry Davy uses electrolysis to isolate the elements sodium and potassium

French chemist Joseph Louis Gay-Lussac shows that when gases combine they do so in simple ratios by volume (later known as his Law of Combining Volumes)

Italian chemist Amedeo Avogadro publishes a hypothesis, about the number of molecules in gases, that becomes known as Avogadro's Law

English chemist William Henry Perkin accidentally creates the first synthetic die, aniline purple (now known as mauve)

English chemist and physicist William Crookes isolates a new element, thallium