Vilfedo Pareto, the turn of the century economist who was convinced that 'there are laws in economics,' and  whose discovery is at the basis of the 80/20 rule.

For Pareto's biorgarphy see http://cepa.newschool.edu/het/profiles/pareto.htm

(from http://cepa.newschool.edu/het/profiles/pareto.htm)
 

Gustav von Schmoller

who was not convinced that there are laws in economy.
For a brief biography, see http://staff-www.uni-marburg.de/~multimed/theorie/ economics/download/schmoller/Schmoller/pdf 

(from http://cepa.newschool.edu/het/profiles/schmoller.htm)
 

The log-log plot showing that webpages on the world wide web have a power law degree distribution from the 1999 Nature paper of Albert, Jeong and Barabasi.
 

The Poisson degree distribution of a random network means that the network is similar to a highway system. In contrast, networks with a power law degree distribution (scale-free) are more similar to the airline routing map: they are held together by a few highly connected hubs.

The Pioneers of the scaling picture in critical phenomena: Leo Kadanoff, as he receives the 1999 National Medal of Science from President Clinton

(from http://www.asee.org/nstmf/html/photos2.htm)

Ben Widom from Cornell University, who has independently uncovered the scaling picture.

(from http://www.chem.cornell.edu/department/Faculty/Widom/widom.html)

Kenneth G. Wilson, who on 1982 was awarded the Nobel Prize for his renormalization group theory for phase transitions.
See Wilson's autobiography written for the occasion of receiving the Nobel prize at http://www.nobel.se/physics/laureates/1982/wilson-autobio.html

(from http://www.physics.ohio-state.edu/~kgw/kgw.html)