Ambrogio Lorenzetti (or Ambruogio Laurati; c. 1290 – June 9, 1348) was an Italian painter of the Sienese school. Events 53 - Roman Emperor Nero marries Claudia Octavia 62 - Claudia Octavia commits Italy (Italia officially the Italian Republic, (Repubblica Italiana is located on the Italian Peninsula in Southern Europe, and on the two largest The Sienese School of Painting flourished in Siena, Italy between the 13th and 15th centuries and for a time rivaled Florence He was active between approximately from 1317 to 1348. His elder brother was the painter Pietro Lorenzetti. Pietro Lorenzetti (or Pietro Laurati; c 1280 - 1348 was an Italian painter active between approximately 1306 and 1345
His work shows the influence of Simone Martini, although more naturalistic. Simone Martini (c 1284 – c 1344 was an Italian painter born in Siena. The earliest dated work of the Sienese painter is a Madonna and Child (1319, Museo Diocesano, San Casciano). His presence was documented in Florentine up until 1321. Florence ( Italian: Firenze Florentia and Fiorenza) is the Capital City of the Italian region of Tuscany He would return there after spending a number of years in Siena. Siena is a city in Tuscany, Italy. It is the capital of the Province of Siena. 
The frescoes on the walls of the Hall of the Nine (Sala dei Nove) or Hall of the Peace (Sala della Pace) in the Palazzo Pubblico of Siena are one of the masterworks of early renaissance secular painting. The Palazzo Pubblico ( town hall) is a palace in the city of Siena, located in the Tuscany region of Italy. The "nine" was the oligarchal assembly of guild and monetary interests that governed the republic. Three walls are painted with frescoes consisting of a large assembly of allegorical figures of virtues in the Allegory of Good Government . In the other two facing panels, Ambrogio weaves panoramic visions of Effects of Good Government on Town and Country, and Allegory of Bad Government and its Effects on Town and Country (also called "Ill-governed Town and Country"). The better preserved "well-governed town and country" is an unrivaled pictorial encyclopedia of incidents in a peaceful medieval "borgo" and coutryside.
The first evidence of the existence of the hourglass can be found in one of his paintings (see external link above). An hourglass, also known as a sandglass, sand timer or sand clock, is a device for the measurement of Time.
Like his brother, he is believed to have died of bubonic plague 1348. Bubonic plague is the best-known manifestation of the bacterial disease plague, caused by the bacterium Yersinia pestis (formerly known as Giorgio Vasari includes a biography of Lorenzetti in his Lives. Giorgio Vasari ( 30 July 1511 – 27 June 1574) was an Italian painter and Architect, who is today famous The Lives of the Most Excellent Painters Sculptors and Architects, or Le Vite delle più eccellenti pittori scultori ed architettori as it was originally known