In the spring, the members of the Program (students, faculty, postdoctoral fellows, technical and administrative staff) travel to an off-campus location for a retreat. The retreat provides time for scientific presentations, informal conversation and social activities. Several of the postdoctoral fellows present brief seminars. Students mount posters describing their thesis projects, and in a relaxed atmosphere observations and technical problems are discussed. An invited scientist gives a talk and participates in the discussions. This scientist also judges the posters and selects students that receive travel awards. The awards are used to defray the cost of attendance at a national or international meeting. Some time is also spent in outdoor activities such as walks and volleyball.